docs: def spawn(self, **kwargs):
          '''Return a new worker for a child process'''
          copy = dict(self.kwargs)
          copy.update(kwargs)
          # Apparently there's an issue with importing gevent in the parent
          # process and then using it int he child. This is meant to relieve that
          # problem by allowing `klass` to be specified as a string.
          if isinstance(self.klass, string_types):
              self.klass = util.import_class(self.klass)
          return self.klass(self.queues, self.client, **copy)