code: def get_packing_plan(self, topologyName, callback=None):
      
      if callback:
        self.packing_plan_watchers[topologyName].append(callback)
      else:
        packing_plan_path = self.get_packing_plan_path(topologyName)
        with open(packing_plan_path) as f:
          data = f.read()
          packing_plan = PackingPlan()
          packing_plan.ParseFromString(data)
docs: get packing plan