code: def shift_right(x, pad_value=None):
    
    if pad_value is None:
      shifted_targets = tf.pad(x, [[0, 0], [1, 0], [0, 0], [0, 0]])[:, :-1, :, :]
    else:
      shifted_targets = tf.concat([pad_value, x], axis=1)[:, :-1, :, :]
    return shifted_targets
docs: Shift the second dimension of x right by one.