us copi function function directli todo action instanc collabor param sourc sourc classifi param target target classifi copi classifi object sourc object target sourc classifi illeg argument except target classifi illeg argument except todo merg multipl inherit necessari current copi common ancestor multipl time copi namespac sourc target copi generaliz element sourc target copi featur featur classifi sourc featur copi featur target 