def _make_message(message_provided, message_otherwise):
    """If message was provided, use it; otherwise, use the alternative one.

    Args:
        message_provided: message to use if provided
        message_otherwise: message to use if the first one was not provided

    Returns:
        First message that evaluates to True

    This function is used by the check_argument() function.

    >>> _make_message(None, 'Otherwise')
    'Otherwise'
    >>> _make_message('Provided', 'Otherwise')
    'Provided'
    """
    __tracebackhide__ = True
    return message_provided or message_otherwise