code: def scale(self, service, count=None, delta=None, **kwargs):
          
          if 'instances' in kwargs:
              count = kwargs.pop('instances')
              warnings.warn("instances is deprecated, use count instead")
          assert not kwargs
          if count is not None and delta is not None:
              raise context.ValueError("cannot specify both `count` and `delta`")
          elif count is None and delta is None:
              raise context.ValueError("must specify either `count` or `delta`")
          if count and count < 0:
              raise context.ValueError("count must be >= 0")
  
          req = proto.ScaleRequest(service_name=service,
                                   count=count,
                                   delta=delta)
          resp = self._call('scale', req)
          return [Container.from_protobuf(c) for c in resp.containers]
docs: Scale a service to a requested number of instances.
  
          Adds or removes containers to match the requested number of instances.
          The number of instances for the service can be specified either as a
          total count or a delta in that count.
  
          When choosing which containers to remove, containers are removed in
          order of state (``WAITING``, ``REQUESTED``, ``RUNNING``) followed by
          age (oldest to newest).
  
          When specified as a negative ``delta``, if the number of removed
          containers is greater than the number of existing containers, all
          containers are removed rather than throwing an error. This means that
          ``app.scale(delta=-1)`` will remove a container if one exists,
          otherwise it will do nothing.
  
          Parameters
          ----------
          service : str
              The service to scale.
          count : int, optional
              The number of instances to scale to.
          delta : int, optional
              The change in number of instances.
  
          Returns
          -------
          containers : list of Container
              A list of containers that were started or stopped.