Called after self-attention. The memory can be updated here.

    Args:
      token: Data returned by pre_attention, which can be used to carry over
        state related to the current memory operation.
      x: a Tensor of data after self-attention and feed-forward
    Returns:
      a (possibly modified) version of the input x

def post_attention(self, token, x):
    """Called after self-attention. The memory can be updated here.

    Args:
      token: Data returned by pre_attention, which can be used to carry over
        state related to the current memory operation.
      x: a Tensor of data after self-attention and feed-forward
    Returns:
      a (possibly modified) version of the input x
    """
    with tf.control_dependencies([
        self.previous_segment.assign(token[0]),
        self.previous_vals.assign(token[1]),
        self.previous_bias.assign(token[2]),
        ]):
      return tf.identity(x)