def _rotate_buff(buff):
    """
    Rotate buffer (for each ``buff[i] = buff[i-1]``).

    Example:
        assert _rotate_buff([1, 2, 3, 4]) == [4, 1, 2, 3]

    Args:
        buff (list): Buffer which will be rotated.

    Returns:
        list: Rotated buffer.
    """
    return [buff[-1]] + buff[:-1]
