def gettext(msg):
    """
    Return the localized translation of message, based on the current global domain, language, and locale directory.
    This function is usually aliased as _() in the local namespace.
    
    @param msg: string
        The key message.
    @return: string
        The translated message.
    """
    assert isinstance(msg, str), 'Invalid key message %s' % msg
    return msg
