Insert a new subclass with filename at index, mockup __module__.

def insert(self, index, filename):
        """Insert a new subclass with filename at index, mockup __module__."""
        base = self._base
        dct = {'__module__': base.__module__, 'filename': filename, '_stack': self}
        cls = type(base.__name__, (base,), dct)

        self._map[cls.filename] = cls
        self._classes.insert(index, cls)