def extract(self, obj, bypass_ref=False):
        """
        Extract parent of obj, according to current token.

        :param obj: the object source
        :param bypass_ref: not used
        """
        for i in range(0, self.stages):
            try:
                obj = obj.parent_obj
            except AttributeError:
                raise UnstagedError(obj, '{!r} must be staged before '
                                         'exploring its parents'.format(obj))
        if self.member:
            return obj.parent_member
        return obj