code: function batchLoaderFunc(graphqlType, serializeRecordKey, getRecords) {
    return keys => getRecords(keys)
      .then(resultArray => getResultsByKey(
        keys, extractAllItems(resultArray), serializeRecordKey, graphqlType,
        { onError: logger }
        )
      );
  }
docs: Key loader function for BatchLoader. Note that serializeBatchLoaderKey has already been passed to BatchLoader as cacheKeyFn