/**
  * Fetch entity data for an array of Google Datastore Keys
  *
  * Consumes the Schema
  * Consumes the Transaction
  *
  * @param \Google_Service_Datastore_Key[] $arr_keys
  * @return mixed
  */
 private function fetchByKeys(array $arr_keys)
 {
     $obj_request = $this->applyTransaction(new \Google_Service_Datastore_LookupRequest());
     $obj_request->setKeys($this->applyNamespace($arr_keys));
     $this->obj_last_response = $this->obj_datasets->lookup($this->str_dataset_id, $obj_request);
     $arr_results = $this->obj_last_response->getFound();
     $arr_mapped_results = $this->createMapper()->mapFromResults($arr_results);
     $this->obj_schema = null;
     // consume Schema
     return $arr_mapped_results;
 }