Check whether given string is a __magic__ Python identifier.
    :return: Whether ``s`` is a __magic__ Python identifier

def is_magic(s):
    """Check whether given string is a __magic__ Python identifier.
    :return: Whether ``s`` is a __magic__ Python identifier
    """
    if not is_identifier(s):
        return False
    return len(s) > 4 and s.startswith('__') and s.endswith('__')