def _create_embedding(self):
        with tf.name_scope('embedding'):
            self.embed_matrix = tf.get_variable(name='embed',
                                                initializer=tf.random_uniform([self.vocab_size, self.embed_dim],
                                                                              minval=-1,
                                                                              maxval=1))
            self.embed = tf.nn.embedding_lookup(self.embed_matrix, self.center_words, name='embedding')