def zero_state(self, sample_batch_shape=()):
    """
    """
    h0 = tf.zeros([1, self.hidden_size])
    c0 = tf.zeros([1, self.hidden_size])
    combined_shape = tf.concat((tf.convert_to_tensor(
        value=sample_batch_shape, dtype=tf.int32), [self.dimensions]),
                               axis=-1)
    previous_output = tf.zeros(combined_shape)
    return previous_output, (h0, c0)