Class introspective

Lib/test/datetimetester.py:4379–4383

        cls = self.theclass
        # A datetime passes itself on, a time passes None.
        class introspective(tzinfo):
            def tzname(self, dt):    return dt and "real" or "none"
            def utcoffset(self, dt):
                return timedelta(minutes = dt and 42 or -42)
            dst = utcoffset

        obj = cls(1, 2, 3, tzinfo=introspective())