Returns a method resolution list of documentation objects
        for `cls`, which must be a documentation object.

        The list will contain objects belonging to `pydoc.Class` or
        `pydoc.External`. Objects belonging to the former are exported
        classes either in this module or in one of its sub-modules.

def mro(self, cls):
        """
        Returns a method resolution list of documentation objects
        for `cls`, which must be a documentation object.

        The list will contain objects belonging to `pydoc.Class` or
        `pydoc.External`. Objects belonging to the former are exported
        classes either in this module or in one of its sub-modules.
        """
        ups = inspect.getmro(cls.cls)
        return list(map(lambda c: self.find_class(c), ups))