code: def create_staging_collection(resource):
      
      ent_cls = get_entity_class(resource)
      coll_cls = get_collection_class(resource)
      agg = StagingAggregate(ent_cls)
      return coll_cls.create_from_aggregate(agg)
docs: Helper function to create a staging collection for the given registered
      resource.
  
      :param resource: registered resource
      :type resource: class implementing or instance providing or subclass of
          a registered resource interface.