docs: def _get_collection_item(collection_id, dataset_id):
      """
          Get a single dataset collection entry by collection ID and dataset ID
          :param collection ID
          :param dataset ID
      """
      collection_item = db.DBSession.query(DatasetCollectionItem).\
              filter(DatasetCollectionItem.collection_id==collection_id,
                     DatasetCollectionItem.dataset_id==dataset_id).first()
      return collection_item