# File lib/tapkit/control/manipulation.rb, line 7
                def add_object_to_property( object, key )
                        to_one, to_many = _keys_with_validation key

                        if to_one.include? key then
                                take_value(key, object)
                        else
                                # search add_to_key method
                                setter = "add_to_#{key}"
                                if respond_to? setter then
                                        __send__(setter, object)
                                else
                                        values = retrieve_value key
                                        unless values.include? object then
                                                values << object
                                        end
                                        take_value(key, object)
                                end
                        end
                end