Modify a standard Stack class (with pop, push, top, isEmpty, size functions implemented) so that when user of a Stack instance modifies the content in the Stack (using pop and push), an error message will be immediately print. You are allowed to add new attribute to the Stack class. Briefly describe how you plan to modify the standard Stack class and provide the complete solution. For instance, if you would like to modify the pop or push function, you need to provide the new versions for them. Hint: think about when you need to check whether some values are modified