Returns all documented module level classes in the module
        sorted alphabetically as a list of `pydoc.Class`.

def classes(self):
        """
        Returns all documented module level classes in the module
        sorted alphabetically as a list of `pydoc.Class`.
        """
        p = lambda o: isinstance(o, Class) and self._docfilter(o)
        return sorted(filter(p, self.doc.values()))