code: def _nextTaskLevel(self):
          
          if not self._last_child:
              self._last_child = self._task_level.child()
          else:
              self._last_child = self._last_child.next_sibling()
          return self._last_child
docs: Return the next C{task_level} for messages within this action.
  
          Called whenever a message is logged within the context of an action.
  
          @return: The message's C{task_level}.