appendix gturtlescreen methods method description screen bgpic(picname=noneset background image or return name of current backgroundimage optional argumentpicname stringname of gif-file or "nopicif picname is filenameset the corresponing image as background if picname is "nopic"delete backgroundimageif present if picname is nonereturn the filename of the current backgroundimage example (for turtlescreen instance named screen)screen bgpic('nopicscreen bgpic("landscape gif"screen bgpic('landscape gifscreen clear(delete all drawings and all turtles from the turtlescreen reset empty turtlescreen to its initial statewhite backgroundno backgroundimageno eventbindings and tracing on example (for turtlescreen instance named screen)screen clear(notethis method is not available as function screen colormode(cmode=nonereturn the colormode or set it to or optional argumentcmode one of the values or rgb values of colortriples have to be in range cmode example (for turtlescreen instance named screen)screen colormode( screen colormode( turtle pencolor( , , screen delay(delay=nonereturn or set the drawing delay in milliseconds optional argumentdelay positive integer example (for turtlescreen instance named screen)screen delay( screen delay( this copy belongs to 'acha