# Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import math
import os
import random
import numpy as np
import paddle
from tqdm import tqdm
from .doc_parser import DocParser
from .log import logger
[文档]def static_params_to_dygraph(model, static_tensor_dict):
"""Simple tool for convert static paramters to dygraph paramters dict.
**NOTE** The model must both support static graph and dygraph mode.
Args:
model (nn.Layer): the model of a neural network.
static_tensor_dict (string): path of which locate the saved paramters in static mode.
Usualy load by `paddle.static.load_program_state`.
Returns:
[tensor dict]: a state dict the same as the dygraph mode.
"""
state_dict = model.state_dict()
# static_tensor_dict = paddle.static.load_program_state(static_params_path)
ret_dict = dict()
for n, p in state_dict.items():
if p.name not in static_tensor_dict:
logger.info("%s paramter is missing from you state dict." % n)
continue
ret_dict[n] = static_tensor_dict[p.name]
return ret_dict
[文档]def dygraph_params_to_static(model, dygraph_tensor_dict, topo=None):
"""Simple tool for convert dygraph paramters to static paramters dict.
**NOTE** The model must both support static graph and dygraph mode.
Args:
model (nn.Layer): the model of a neural network.
dygraph_tensor_dict (string): path of which locate the saved paramters in static mode.
Returns:
[tensor dict]: a state dict the same as the dygraph mode.
"""
state_dict = model.state_dict()
ret_dict = dict()
for name, parm in state_dict.items():
if name not in dygraph_tensor_dict:
logger.info("%s paramter is missing from you state dict." % name)
continue
tensor = dygraph_tensor_dict[name]
if parm.is_distributed:
assert topo is not None
for dim, v in enumerate(tensor.shape):
if parm.shape[dim] != v:
break
splited = np.split(tensor, topo.mp_info.size, axis=dim)[topo.mp_info.rank]
ret_dict[parm.name] = splited
else:
ret_dict[parm.name] = tensor
return ret_dict
[文档]class TimeCostAverage(object):
"""
Simple tool for calcluating time average cost in the process of training and inferencing.
"""
def __init__(self):
self.reset()
[文档] def reset(self):
"""
Reset the recoder state, and reset the `cnt` to zero.
"""
self.cnt = 0
self.total_time = 0
[文档] def record(self, usetime):
"""
Recoding the time cost in current step and accumulating the `cnt`.
"""
self.cnt += 1
self.total_time += usetime
[文档] def get_average(self):
"""
Returning the average time cost after the start of training.
"""
if self.cnt == 0:
return 0
return self.total_time / self.cnt
[文档]def get_env_device():
"""
Return the device name of running enviroment.
"""
if paddle.is_compiled_with_cuda():
return "gpu"
elif "npu" in paddle.device.get_all_custom_device_type():
return "npu"
elif paddle.is_compiled_with_rocm():
return "rocm"
elif paddle.is_compiled_with_xpu():
return "xpu"
return "cpu"
[文档]def compare_version(version, pair_version):
"""
Args:
version (str): The first version string needed to be compared.
The format of version string should be as follow : "xxx.yyy.zzz".
pair_version (str): The second version string needed to be compared.
The format of version string should be as follow : "xxx.yyy.zzz".
Returns:
int: The result of comparasion. 1 means version > pair_version; 0 means
version = pair_version; -1 means version < pair_version.
Examples:
>>> compare_version("2.2.1", "2.2.0")
>>> 1
>>> compare_version("2.2.0", "2.2.0")
>>> 0
>>> compare_version("2.2.0-rc0", "2.2.0")
>>> -1
>>> compare_version("2.3.0-rc0", "2.2.0")
>>> 1
"""
version = version.strip()
pair_version = pair_version.strip()
if version == pair_version:
return 0
version_list = version.split(".")
pair_version_list = pair_version.split(".")
for version_code, pair_version_code in zip(version_list, pair_version_list):
if not version_code.isnumeric():
return -1
if not pair_version_code.isnumeric():
return 1
if int(version_code) > int(pair_version_code):
return 1
elif int(version_code) < int(pair_version_code):
return -1
return 0
[文档]def get_bool_ids_greater_than(probs, limit=0.5, return_prob=False):
"""
Get idx of the last dimension in probability arrays, which is greater than a limitation.
Args:
probs (List[List[float]]): The input probability arrays.
limit (float): The limitation for probability.
return_prob (bool): Whether to return the probability
Returns:
List[List[int]]: The index of the last dimension meet the conditions.
"""
probs = np.array(probs)
dim_len = len(probs.shape)
if dim_len > 1:
result = []
for p in probs:
result.append(get_bool_ids_greater_than(p, limit, return_prob))
return result
else:
result = []
for i, p in enumerate(probs):
if p > limit:
if return_prob:
result.append((i, p))
else:
result.append(i)
return result
[文档]def get_span(start_ids, end_ids, with_prob=False):
"""
Get span set from position start and end list.
Args:
start_ids (List[int]/List[tuple]): The start index list.
end_ids (List[int]/List[tuple]): The end index list.
with_prob (bool): If True, each element for start_ids and end_ids is a tuple aslike: (index, probability).
Returns:
set: The span set without overlapping, every id can only be used once .
"""
if with_prob:
start_ids = sorted(start_ids, key=lambda x: x[0])
end_ids = sorted(end_ids, key=lambda x: x[0])
else:
start_ids = sorted(start_ids)
end_ids = sorted(end_ids)
start_pointer = 0
end_pointer = 0
len_start = len(start_ids)
len_end = len(end_ids)
couple_dict = {}
while start_pointer < len_start and end_pointer < len_end:
if with_prob:
start_id = start_ids[start_pointer][0]
end_id = end_ids[end_pointer][0]
else:
start_id = start_ids[start_pointer]
end_id = end_ids[end_pointer]
if start_id == end_id:
couple_dict[end_ids[end_pointer]] = start_ids[start_pointer]
start_pointer += 1
end_pointer += 1
continue
if start_id < end_id:
couple_dict[end_ids[end_pointer]] = start_ids[start_pointer]
start_pointer += 1
continue
if start_id > end_id:
end_pointer += 1
continue
result = [(couple_dict[end], end) for end in couple_dict]
result = set(result)
return result
[文档]class DataConverter(object):
"""DataConverter to convert data export from annotation platform"""
def __init__(
self,
label_studio_file,
negative_ratio=5,
prompt_prefix="情感倾向",
options=["正向", "负向"],
separator="##",
layout_analysis=False,
expand_to_a4_size=True,
schema_lang="ch",
ocr_lang="en",
anno_type="text",
):
"""Init Data Converter"""
self.negative_ratio = negative_ratio
self.prompt_prefix = prompt_prefix
self.options = options
self.separator = separator
self.layout_analysis = layout_analysis
self.expand_to_a4_size = expand_to_a4_size
self.schema_lang = schema_lang
self.ocr_lang = ocr_lang
self.anno_type = anno_type
self.label_studio_file = label_studio_file
self.ignore_list = ["属性值", "object"]
def process_text_tag(self, line, task_type="ext"):
items = {}
items["text"] = line["data"]["text"]
if task_type == "ext":
items["entities"] = []
items["relations"] = []
result_list = line["annotations"][0]["result"]
for a in result_list:
if a["type"] == "labels":
items["entities"].append(
{
"id": a["id"],
"start_offset": a["value"]["start"],
"end_offset": a["value"]["end"],
"label": a["value"]["labels"][0],
}
)
else:
items["relations"].append(
{
"id": a["from_id"] + "-" + a["to_id"],
"from_id": a["from_id"],
"to_id": a["to_id"],
"type": a["labels"][0],
}
)
elif task_type == "cls":
items["label"] = line["annotations"][0]["result"][0]["value"]["choices"]
return items
def process_image_tag(self, line, task_type="ext"):
def _io1(box1, box2):
"""calc intersection over box1 area"""
x1 = max(box1[0], box2[0])
y1 = max(box1[1], box2[1])
x2 = min(box1[2], box2[2])
y2 = min(box1[3], box2[3])
if x2 <= x1 or y2 <= y1:
return 0.0
box1_area = (box1[2] - box1[0]) * (box1[3] - box1[1])
return (x2 - x1) * (y2 - y1) * 1.0 / box1_area
def _find_segment_in_box(layouts, box, threshold=0.7):
positions = []
global_offset = 0
for segment in layouts:
sbox = segment[0]
text_len = len(segment[1])
if text_len == 0:
continue
if len(segment) == 2 or (len(segment) == 3 and segment[2] != "table"):
char_w = (sbox[2] - sbox[0]) * 1.0 / text_len
for i in range(text_len):
cbox = [sbox[0] + i * char_w, sbox[1], sbox[0] + (i + 1) * char_w, sbox[3]]
c_covered = _io1(cbox, box)
if c_covered >= threshold:
positions.append(global_offset)
elif (
cbox[2] == min(cbox[2], box[2])
and cbox[0] == max(cbox[0], box[0])
and cbox[1] < box[1]
and cbox[3] > box[3]
):
if c_covered > 0.5:
positions.append(global_offset)
global_offset += 1
else:
cell_covered = _io1(box, sbox)
if cell_covered >= threshold:
for i in range(text_len):
positions.append(global_offset)
global_offset += 1
else:
global_offset += text_len
offsets = []
if not positions:
return offsets
spos = positions[0]
for i in range(1, len(positions)):
if positions[i] != positions[i - 1] + 1:
offsets.append((spos, positions[i - 1] + 1))
spos = positions[i]
offsets.append((spos, positions[-1] + 1))
return offsets
items = {}
img_file = os.path.basename(line["data"]["image"])
p = img_file.find("-")
img_file = img_file[p + 1 :]
img_path = os.path.join("/".join(self.label_studio_file.split("/")[:-1]), "images", img_file)
if not os.path.exists(img_path):
logger.warning(
"Image file %s not exist in %s"
% (img_file, "/".join(self.label_studio_file.split("/")[:-1]) + "images")
)
return None
logger.info("Parsing image file %s ..." % (img_file))
doc_parser = DocParser(layout_analysis=self.layout_analysis, ocr_lang=self.ocr_lang)
parsed_doc = doc_parser.parse({"doc": img_path})
img_w, img_h = parsed_doc["img_w"], parsed_doc["img_h"]
text = ""
bbox = []
for segment in parsed_doc["layout"]:
box = doc_parser._normalize_box(segment[0], [img_w, img_h], [1000, 1000])
text += segment[1]
bbox.extend([box] * len(segment[1]))
assert len(text) == len(bbox), "len of text is not equal to len of bbox"
items["text"] = text
items["bbox"] = bbox
items["image"] = parsed_doc["image"]
if task_type == "ext":
items["entities"] = []
items["relations"] = []
result_list = line["annotations"][0]["result"]
ent_ids = []
for e in result_list:
if e["type"] != "rectanglelabels":
continue
assert img_w == e["original_width"] and img_h == e["original_height"], "Image size not match"
box = [
e["value"]["x"] * 0.01 * img_w,
e["value"]["y"] * 0.01 * img_h,
(e["value"]["x"] + e["value"]["width"]) * 0.01 * img_w,
(e["value"]["y"] + e["value"]["height"]) * 0.01 * img_h,
]
offsets = _find_segment_in_box(parsed_doc["layout"], box)
if len(offsets) > 0:
items["entities"].append(
{
"id": e["id"],
"start_offset": offsets[0][0],
"end_offset": offsets[0][1],
"label": e["value"]["rectanglelabels"][0],
}
)
ent_ids.append(e["id"])
for r in result_list:
if r["type"] != "relation":
continue
if r["from_id"] in ent_ids and r["to_id"] in ent_ids:
items["relations"].append(
{
"id": r["from_id"] + "-" + r["to_id"],
"from_id": r["from_id"],
"to_id": r["to_id"],
"type": r["labels"][0],
}
)
else:
items["label"] = line["annotations"][0]["result"][0]["value"]["choices"]
return items
[文档] def convert_cls_examples(self, raw_examples):
"""
Convert labeled data for classification task.
"""
examples = []
logger.info("Converting annotation data...")
with tqdm(total=len(raw_examples)):
for line in raw_examples:
if self.anno_type == "text":
items = self.process_text_tag(line, task_type="cls")
image, bbox = None, None
elif self.anno_type == "image":
items = self.process_image_tag(line, task_type="cls")
if items is None:
continue
image, bbox = items["image"], items["bbox"]
else:
raise ValueError("The type of annotation should be text or image")
text, labels = items["text"], items["label"]
example = self.generate_cls_example(text, labels, self.prompt_prefix, self.options, image, bbox)
examples.append(example)
return examples
[文档] def convert_ext_examples(self, raw_examples, is_train=True):
"""
Convert labeled data for extraction task.
"""
def _sep_cls_label(label, separator):
label_list = label.split(separator)
if len(label_list) == 1:
return label_list[0], None
return label_list[0], label_list[1:]
texts = []
# {"content": "", "result_list": [], "prompt": "X"}
entity_examples = []
# {"content": "", "result_list": [], "prompt": "X的Y"}
relation_examples = []
# {"content": "", "result_list": [], "prompt": "X的情感倾向[正向，负向]"}
entity_cls_examples = []
# Entity label set: ["时间", "地点", ... ]
entity_label_set = []
# Entity name set: ["2月8日上午", "北京", ... ]
entity_name_set = []
# Predicate set: ["歌手", "所属专辑", ... ]
predicate_set = []
# List[List[str]]
# List of entity prompt for each example
entity_prompt_list = []
# List of relation prompt for each example
relation_prompt_list = []
# Golden subject label for each example
subject_golden_list = []
# List of inverse relation for each example
inverse_relation_list = []
# List of predicate for each example
predicate_list = []
if self.anno_type == "text":
images, bbox_list = None, None
else:
images, bbox_list = [], []
logger.info("Converting annotation data...")
with tqdm(total=len(raw_examples)) as pbar:
for line in raw_examples:
if self.anno_type == "text":
items = self.process_text_tag(line, task_type="ext")
image, bbox = None, None
elif self.anno_type == "image":
items = self.process_image_tag(line, task_type="ext")
if items is None:
continue
image, bbox = items["image"], items["bbox"]
images.append(image)
bbox_list.append(bbox)
else:
raise ValueError("The type of annotation should be text or image")
text, relations, entities = items["text"], items["relations"], items["entities"]
texts.append(text)
entity_example = []
entity_prompt = []
entity_example_map = {}
entity_map = {} # id to entity name
for entity in entities:
entity_name = text[entity["start_offset"] : entity["end_offset"]]
entity_map[entity["id"]] = {
"name": entity_name,
"start": entity["start_offset"],
"end": entity["end_offset"],
}
if entity["label"] in self.ignore_list:
continue
entity_label, entity_cls_label = _sep_cls_label(entity["label"], self.separator)
# Define the prompt prefix for entity-level classification
# xxx + "的" + 情感倾向 -> Chinese
# Sentiment classification + " of " + xxx -> English
if self.schema_lang == "ch":
entity_cls_prompt_prefix = entity_name + "的" + self.prompt_prefix
else:
entity_cls_prompt_prefix = self.prompt_prefix + " of " + entity_name
if entity_cls_label is not None:
entity_cls_example = self.generate_cls_example(
text, entity_cls_label, entity_cls_prompt_prefix, self.options, image, bbox
)
entity_cls_examples.append(entity_cls_example)
result = {"text": entity_name, "start": entity["start_offset"], "end": entity["end_offset"]}
if entity_label not in entity_example_map.keys():
entity_example_map[entity_label] = {
"content": text,
"result_list": [result],
"prompt": entity_label,
}
if self.anno_type == "image":
entity_example_map[entity_label]["image"] = image
entity_example_map[entity_label]["bbox"] = bbox
else:
entity_example_map[entity_label]["result_list"].append(result)
if entity_label not in entity_label_set and entity_label != "观点词":
entity_label_set.append(entity_label)
if entity_name not in entity_name_set:
entity_name_set.append(entity_name)
entity_prompt.append(entity_label)
for v in entity_example_map.values():
entity_example.append(v)
entity_examples.append(entity_example)
entity_prompt_list.append(entity_prompt)
subject_golden = [] # Golden entity inputs
relation_example = []
relation_prompt = []
relation_example_map = {}
inverse_relation = []
predicates = []
for relation in relations:
predicate = relation["type"]
subject_id = relation["from_id"]
object_id = relation["to_id"]
# The relation prompt is constructed as follows:
# subject + "的" + predicate -> Chinese
# predicate + " of " + subject -> English
if self.schema_lang == "ch":
prompt = entity_map[subject_id]["name"] + "的" + predicate
inverse_negative = entity_map[object_id]["name"] + "的" + predicate
else:
prompt = predicate + " of " + entity_map[subject_id]["name"]
inverse_negative = predicate + " of " + entity_map[object_id]["name"]
if entity_map[subject_id]["name"] not in subject_golden:
subject_golden.append(entity_map[subject_id]["name"])
result = {
"text": entity_map[object_id]["name"],
"start": entity_map[object_id]["start"],
"end": entity_map[object_id]["end"],
}
inverse_relation.append(inverse_negative)
predicates.append(predicate)
if prompt not in relation_example_map.keys():
relation_example_map[prompt] = {"content": text, "result_list": [result], "prompt": prompt}
if self.anno_type == "image":
relation_example_map[prompt]["image"] = image
relation_example_map[prompt]["bbox"] = bbox
else:
relation_example_map[prompt]["result_list"].append(result)
if predicate not in predicate_set:
predicate_set.append(predicate)
relation_prompt.append(prompt)
for v in relation_example_map.values():
relation_example.append(v)
relation_examples.append(relation_example)
relation_prompt_list.append(relation_prompt)
subject_golden_list.append(subject_golden)
inverse_relation_list.append(inverse_relation)
predicate_list.append(predicates)
pbar.update(1)
logger.info("Adding negative samples for first stage prompt...")
positive_examples, negative_examples = self.add_entity_negative_example(
entity_examples, texts, entity_prompt_list, entity_label_set, images, bbox_list
)
if len(positive_examples) == 0:
all_entity_examples = []
else:
all_entity_examples = positive_examples + negative_examples
all_relation_examples = []
if len(predicate_set) != 0:
logger.info("Adding negative samples for second stage prompt...")
if is_train:
positive_examples = []
negative_examples = []
per_n_ratio = self.negative_ratio // 3
with tqdm(total=len(texts)) as pbar:
for i, text in enumerate(texts):
negative_example = []
collects = []
num_positive = len(relation_examples[i])
# 1. inverse_relation_list
redundants1 = inverse_relation_list[i]
# 2. entity_name_set ^ subject_golden_list[i]
redundants2 = []
if len(predicate_list[i]) != 0:
nonentity_list = list(set(entity_name_set) ^ set(subject_golden_list[i]))
nonentity_list.sort()
if self.schema_lang == "ch":
redundants2 = [
nonentity + "的" + predicate_list[i][random.randrange(len(predicate_list[i]))]
for nonentity in nonentity_list
]
else:
redundants2 = [
predicate_list[i][random.randrange(len(predicate_list[i]))] + " of " + nonentity
for nonentity in nonentity_list
]
# 3. entity_label_set ^ entity_prompt_list[i]
redundants3 = []
if len(subject_golden_list[i]) != 0:
non_ent_label_list = list(set(entity_label_set) ^ set(entity_prompt_list[i]))
non_ent_label_list.sort()
if self.schema_lang == "ch":
redundants3 = [
subject_golden_list[i][random.randrange(len(subject_golden_list[i]))]
+ "的"
+ non_ent_label
for non_ent_label in non_ent_label_list
]
else:
redundants3 = [
non_ent_label
+ " of "
+ subject_golden_list[i][random.randrange(len(subject_golden_list[i]))]
for non_ent_label in non_ent_label_list
]
redundants_list = [redundants1, redundants2, redundants3]
for redundants in redundants_list:
if self.anno_type == "text":
added, rest = self.add_relation_negative_example(
redundants,
texts[i],
num_positive,
per_n_ratio,
)
else:
added, rest = self.add_relation_negative_example(
redundants, texts[i], num_positive, per_n_ratio, images[i], bbox_list[i]
)
negative_example.extend(added)
collects.extend(rest)
num_sup = num_positive * self.negative_ratio - len(negative_example)
if num_sup > 0 and collects:
if num_sup > len(collects):
idxs = [k for k in range(len(collects))]
else:
idxs = random.sample(range(0, len(collects)), num_sup)
for idx in idxs:
negative_example.append(collects[idx])
positive_examples.extend(relation_examples[i])
negative_examples.extend(negative_example)
pbar.update(1)
all_relation_examples = positive_examples + negative_examples
else:
relation_examples = self.add_full_negative_example(
relation_examples, texts, relation_prompt_list, predicate_set, subject_golden_list
)
all_relation_examples = [r for relation_example in relation_examples for r in relation_example]
return all_entity_examples + all_relation_examples + entity_cls_examples
def generate_cls_example(self, text, labels, prompt_prefix, options, image=None, bbox=None):
random.shuffle(self.options)
cls_options = ",".join(self.options)
prompt = prompt_prefix + "[" + cls_options + "]"
result_list = []
example = {"content": text, "result_list": result_list, "prompt": prompt}
if image and bbox:
example["image"] = image
example["bbox"] = bbox
for label in labels:
start = prompt.rfind(label) - len(prompt) - 1
end = start + len(label)
result = {"text": label, "start": start, "end": end}
example["result_list"].append(result)
return example
def add_full_negative_example(
self, examples, texts, relation_prompt_list, predicate_set, subject_golden_list, images=None, bbox_list=None
):
with tqdm(total=len(relation_prompt_list)) as pbar:
for i, relation_prompt in enumerate(relation_prompt_list):
negative_sample = []
for subject in subject_golden_list[i]:
for predicate in predicate_set:
# The relation prompt is constructed as follows:
# subject + "的" + predicate -> Chinese
# predicate + " of " + subject -> English
if self.schema_lang == "ch":
prompt = subject + "的" + predicate
else:
prompt = predicate + " of " + subject
if prompt not in relation_prompt:
negative_result = {"content": texts[i], "result_list": [], "prompt": prompt}
if images and bbox_list:
negative_result["image"] = images[i]
negative_result["bbox"] = bbox_list[i]
negative_sample.append(negative_result)
examples[i].extend(negative_sample)
pbar.update(1)
return examples
def add_entity_negative_example(self, examples, texts, prompts, label_set, images=None, bbox_list=None):
negative_examples = []
positive_examples = []
with tqdm(total=len(prompts)) as pbar:
for i, prompt in enumerate(prompts):
redundants = list(set(label_set) ^ set(prompt))
redundants.sort()
num_positive = len(examples[i])
if num_positive != 0:
actual_ratio = math.ceil(len(redundants) / num_positive)
else:
# Set num_positive to 1 for text without positive example
num_positive, actual_ratio = 1, 0
if actual_ratio <= self.negative_ratio or self.negative_ratio == -1:
idxs = [k for k in range(len(redundants))]
else:
idxs = random.sample(range(0, len(redundants)), self.negative_ratio * num_positive)
for idx in idxs:
negative_result = {"content": texts[i], "result_list": [], "prompt": redundants[idx]}
if images and bbox_list:
negative_result["image"] = images[i]
negative_result["bbox"] = bbox_list[i]
negative_examples.append(negative_result)
positive_examples.extend(examples[i])
pbar.update(1)
return positive_examples, negative_examples
def add_relation_negative_example(self, redundants, text, num_positive, ratio, image=None, bbox=None):
added_example = []
rest_example = []
if num_positive != 0:
actual_ratio = math.ceil(len(redundants) / num_positive)
else:
# Set num_positive to 1 for text without positive example
num_positive, actual_ratio = 1, 0
all_idxs = [k for k in range(len(redundants))]
if actual_ratio <= ratio or ratio == -1:
idxs = all_idxs
rest_idxs = []
else:
idxs = random.sample(range(0, len(redundants)), ratio * num_positive)
rest_idxs = list(set(all_idxs) ^ set(idxs))
for idx in idxs:
negative_result = {"content": text, "result_list": [], "prompt": redundants[idx]}
if image and bbox:
negative_result["image"] = image
negative_result["bbox"] = bbox
added_example.append(negative_result)
for rest_idx in rest_idxs:
negative_result = {"content": text, "result_list": [], "prompt": redundants[rest_idx]}
if image and bbox:
negative_result["image"] = image
negative_result["bbox"] = bbox
rest_example.append(negative_result)
return added_example, rest_example