docs: def pop(self):
          """Removes the topmost item from the stack, will return the
          old value or `None` if the stack was already empty.
          """
          stack = getattr(self._local, "stack", None)
          if stack is None:
              return None
          elif len(stack) == 1:
              release_local(self._local)
              return stack[-1]
          else:
              return stack.pop()