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Simple BERT-Based Sentence Classification with Keras / TensorFlow 2

Simple BERT-Based Sentence Classification with Keras / TensorFlow 2

ernie

Simple BERT-Based Sentence Classification with Keras / TensorFlow 2. Built with HuggingFace's Transformers.

Installation

pip install ernie

Open In Colab

Fine-Tuning

Sentence Classification

from ernie import SentenceClassifier, Models
import pandas as pd

tuples = [("This is a positive example. I'm very happy today.", 1),
          ("This is a negative sentence. Everything was wrong today at work.", 0)]

df = pd.DataFrame(tuples)
classifier = SentenceClassifier(model_name=Models.BertBaseUncased, max_length=128, labels_no=2)
classifier.load_dataset(df, validation_split=0.2)
classifier.fine_tune(epochs=4, learning_rate=2e-5, training_batch_size=32, validation_batch_size=64)

Prediction

Predict a single text

text = "Oh, that's great!"

# It returns a tuple with the prediction
probabilities = classifier.predict_one(text)

Predict multiple texts

texts = ["Oh, that's great!", "That's really bad"]

# It returns a generator of tuples with the predictions
probabilities = classifier.predict(texts)

Prediction Strategies

If the length in tokens of the texts is greater than the max_length with which the model has been fine-tuned, they will be truncated. To avoid losing information you can use a split strategy and aggregate the predictions in different ways.

Split Strategies

  • SentencesWithoutUrls. The text will be splitted in sentences.
  • GroupedSentencesWithoutUrls. The text will be splitted in groups of sentences with a length in tokens similar to max_length.

Aggregation Strategies

  • Mean: the prediction of the text will be the mean of the predictions of the splits.
  • MeanTopFiveBinaryClassification: the mean is computed over the 5 higher predictions only.
  • MeanTopTenBinaryClassification: the mean is computed over the 10 higher predictions only.
  • MeanTopFifteenBinaryClassification: the mean is computed over the 15 higher predictions only.
  • MeanTopTwentyBinaryClassification: the mean is computed over the 20 higher predictions only.
from ernie import SplitStrategies, AggregationStrategies

texts = ["Oh, that's great!", "That's really bad"]
probabilities = classifier.predict(texts,
                                   split_strategy=SplitStrategies.GroupedSentencesWithoutUrls,
                                   aggregation_strategy=AggregationStrategies.Mean) 

You can define your custom strategies through AggregationStrategy and SplitStrategy classes.

from ernie import SplitStrategy, AggregationStrategy

my_split_strategy = SplitStrategy(split_patterns: list, remove_patterns: list, remove_too_short_groups: bool, group_splits: bool)
my_aggregation_strategy = AggregationStrategy(method: function, max_items: int, top_items: bool, sorting_class_index: int)

Save and restore a fine-tuned model

Save model

classifier.dump('./model')

Load model

classifier = SentenceClassifier(model_path='./model')

Additional Info

Accesing the model and tokenizer

You can directly access both the model and tokenizer objects once the classifier has been instantiated:

classifier.model
classifier.tokenizer

Keras model.fit arguments

You can pass Keras arguments of the model.fit method to the classifier.fine_tune method. For example:

classifier.fine_tune(class_weight={0: 0.2, 1: 0.8})

Supported Models

BERT

  • BertBaseUncased
  • BertBaseCased
  • BertLargeUncased
  • BertLargeCased

RoBERTa

  • RobertaBaseCased
  • RobertaLargeCased

XLNet

  • XLNetBaseCased
  • XLNetLargeCased

DistilBERT

  • DistilBertBaseUncased
  • DistilBertBaseMultilingualCased

GitHub

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