Whitelist *what*.

    :param what: What to whitelist.
    :type what: :class:`list` of :class:`type` or :class:`attr.Attribute`\\ s

    :rtype: :class:`callable`

def include(*what):
    """
    Whitelist *what*.

    :param what: What to whitelist.
    :type what: :class:`list` of :class:`type` or :class:`attr.Attribute`\\ s

    :rtype: :class:`callable`
    """
    cls, attrs = _split_what(what)

    def include_(attribute, value):
        return value.__class__ in cls or attribute in attrs

    return include_