docs: def participating_ecs(self):
          '''A list of the execution contexts this component is participating in.
  
          '''
          with self._mutex:
              if not self._participating_ecs:
                  self._participating_ecs = [ExecutionContext(ec,
                                      self._obj.get_context_handle(ec)) \
                               for ec in self._obj.get_participating_contexts()]
          return self._participating_ecs