# File lib/tapkit/control/manipulation.rb, line 27
                def remove_object_from_both_sides_of_relationship( object, key )
                        to_one, to_many = _keys_with_validation key

                        # update this side
                        if to_many.include? key then
                                remove_object_from_property(object, key)
                        else
                                # set nil to to-one relationship
                                add_object_to_property(nil, key)
                        end

                        # update the another side
                        unless backrel = inverse(key) then
                                return
                        end

                        dest_cd = class_description.class_description key
                        if dest_cd.to_many_relationship_keys.include? backrel then
                                object.remove_object_from_property(self, backrel)
                        else
                                object.add_object_to_property(nil, backrel)
                        end
                end