Write a method called mirror that doubles the size of a list by appending the mirror image of the original sequence to the end of the list. The mirror image is the same sequence of values in reverse order. For example, if a variable called list stores [1, 3, 2, 7] and the client calls list.mirror(); then the list should be changed to store [1, 3, 2, 7, 7, 2, 3, 1]. Notice that it has doubled in size because the original sequence now appears in reverse order at the end of the list.