def generic_args(t):
    """
    Generic's arg-types
    >>> generic_args(list) is None
    True
    >>> generic_args(Dict) is None
    True
    >>> generic_args(List[str])
    (<class 'str'>,)
    >>> generic_args(Union[str, int, None])
    (<class 'str'>, <class 'int'>, <class 'NoneType'>)
    >>> generic_args(Union[int, str, None])
    (<class 'int'>, <class 'str'>, <class 'NoneType'>)
    """
    if hasattr(t, '__origin__') and hasattr(t, '__args__'):
        return getattr(t, '__args__')
    else:
        return None
