# Source code for nlp_architect.nn.tensorflow.python.keras.callbacks

    # ******************************************************************************
    # Copyright 2017-2018 Intel Corporation
    #
    # 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.
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    from __future__ import division
    from __future__ import print_function
    from __future__ import unicode_literals
    from __future__ import absolute_import

    import tensorflow as tf

    from nlp_architect.utils.metrics import get_conll_scores

    class ConllCallback(tf.keras.callbacks.Callback):
        """
        A Tensorflow(Keras) Conlleval evaluator.
        Runs the conlleval script for given x and y inputs.
        Prints Conlleval F1 score on the end of each epoch.

        Args:
            x: features matrix
            y: labels matrix
            y_vocab (dict): int-to-str labels lexicon
            batch_size (:obj:`int`, optional): batch size
        """

        def __init__(self, x, y, y_vocab, batch_size=1):
            super(ConllCallback, self).__init__()
            self.x = x
            self.y = y
            self.y_vocab = {v: k for k, v in y_vocab.items()}
            self.bsz = batch_size

        def on_epoch_end(self, epoch, logs=None):
            predictions = self.model.predict(self.x, batch_size=self.bsz)
            stats = get_conll_scores(predictions, self.y, self.y_vocab)
            print()
            print("Conll eval: \n{}".format(stats))