python programming container class to further enhance our drawing program we will first create data structure to hold all of our drawing commands this is our first example of defining our own class in this text so we'll go slow and provide lot of detail about what is happening and why to begin let' figure out what we want to do with this container class our program will begin by creating an empty container to do thiswe'll write line like this graphicscommands pylist(thenwe will want to add graphics commands to our list using an append method like this command gotocommand(xywidthcolorgraphicscommands append(commandwe would also like to be able to iterate over the commands in our list for command in graphicscommandsdraw each command on the screen using the turtle called command draw(tat this pointour container class looks lot like list we are defining our own list class to illustrate first data structure and to motivate discussion of how lists can be implemented efficiently in this and the next polymorphism one important concept in object-oriented programming is called polymorphism the word polymorphic literally means many forms as this concept is applied to computer programmingthe idea is that there can be many ways that particular behavior might be implemented in relationship to our pylist container class that we are buildingthe idea is that each type of graphics command will know how to draw itself correctly for instanceone type of graphics command is the gotocommand when gotocommand is drawn it draws line on the screen from the current point to some new ( ,ycoordinate butwhen circlecommand is drawnit draws circle on the screen with particular radius this polymorphic behavior can be defined by creating class and draw method for each different type of behavior the code in sect is collection of classes that define the polymorphic behavior of the different graphics draw methods there is one class for each drawing command that will be processed by the program this copy belongs to 'acha