def generate_window_sequence(self, sentence_ix, sentence, label):
    window_sequences = []
    offset = int(self.window_size/2)
    ws = tf.strings.split([sentence], sep=' ').values
    ls = ws.get_shape()[0].value
    print(ls)
    for i in range(offset, ls-offset):

      window_sequences.append((tf.gather_nd(ws, [i-offset]), tf.gather_nd(ws, [i]) ))
      window_sequences.append((tf.gather_nd(ws, [i+offset]), tf.gather_nd(ws, [i]) ))