code: def pop(self):
          
          popped = False
          result = None
          current_node = self._first_node
          while not popped:
              next_node = current_node.next()
              next_next_node = next_node.next()
              if not next_next_node:
                  self._last_node = current_node
                  self._last_node.update_next(None)
                  self._size -= 1
                  result = next_node.data()
                  popped = True
              current_node = next_node
          return result
docs: Removes the last node from the list