of *factory*.

    :param default: Value to be used if ``None`` is passed. Passing an instance
       of `attr.Factory` is supported, however the ``takes_self`` option
       is *not*.
    :param callable factory: A callable that takes not parameters whose result
       is used if ``None`` is passed.

    :raises TypeError: If **neither** *default* or *factory* is passed.
    :raises TypeError: If **both** *default* and *factory* are passed.
    :raises ValueError: If an instance of `attr.Factory` is passed with
       ``takes_self=True``.

    .. versionadded:: 18.2.0
    Nz(Must pass either `default` or `factory`.z5Must pass either `default` or `factory` but not both.z1`takes_self` is not supported by default_if_none.c