code: def _get_composition_collection(self, composition_id):
          
          collection = JSONClientValidated('repository',
                                           collection='Composition',
                                           runtime=self._runtime)
          composition_map = collection.find_one({'_id': ObjectId(composition_id.get_identifier())})
          if 'assetIds' not in composition_map:
              raise errors.NotFound('no Assets are assigned to this Composition')
          return composition_map, collection
docs: Returns a Mongo Collection and Composition given a Composition Id