code: def get_runtime(self):
          
          if self.start is None: return None
  
          if self.end is None:
              delta = datetime.datetime.now() - self.start
          else:
              delta = self.end - self.start
  
          return MyTimedelta.as_timedelta(delta)
docs: :class:`timedelta` with the run-time, None if the Task is not running