docs: def spawn(self, owner, *args, **kwargs):
          """Spawns a new subordinate actor of `owner` and stores it in this container.
  
          jobs = Container()
          ...
          jobs.spawn(self, Job)
          jobs.spawn(self, Job, some_param=123)
  
          jobs = Container(Job)
          ...
          jobs.spawn(self)
          jobs.spawn(self, some_param=123)
  
          jobs = Container(Job.using('abc', some_kwarg=321))
          ...
          jobs.spawn(self, extra_kwarg=123)
          jobs.spawn(self, some_kwarg=123, extra_kwarg=123)
          jobs.spawn(self, 'xyz', some_kwarg=345, extra_kwarg=567)
  
          """
          return (self._spawn(owner, self.factory, *args, **kwargs)
                  if self.factory else
                  self._spawn(owner, *args, **kwargs))