code: def pop(self):
          
          if len(self.stack):
              popped = self.stack.pop()
              log.debug('pop: (%s)\n%s', Repr(popped), Repr(self.stack))
              return popped
          else:
              log.debug('stack empty, not-popped')
          return None
docs: Pop the frame at the top of the stack.
          @return: The popped frame, else None.
          @rtype: L{Frame}