extend build extend object abas object anextens object apoint us base us abas us extens us anextens extens point point extens point apoint base extens illeg argument except base usecas extens usecas base equal extens illeg argument except base usecas extens usecas differ point base extens point contain point illeg argument except extensionpoint base usecas point build extens point base extend extend creat extend extend set base base extend set extens extens extend extens point add point extend 