Pop and Peek

Now that we can add items to our stack, we need to be able to view the top item, and remove the top item.

Assignment

Complete the peek method. It should return the top item from the stack without modifying the stack. If the stack is empty, return None.
Complete the pop method. It should remove and return the top item from the stack. If the stack is empty, return None.

Tips

The del keyword can be used to remove an item from a list by index.
The last item in a Python list can be accessed with the index -1.