code: public function executeOperation(ServerConfig $config, OperationParams $op)
      {
          $promiseAdapter = $config->getPromiseAdapter() ?: Executor::getPromiseAdapter();
          $result         = $this->promiseToExecuteOperation($promiseAdapter, $config, $op);
  
          if ($promiseAdapter instanceof SyncPromiseAdapter) {
              $result = $promiseAdapter->wait($result);
          }
  
          return $result;
      }
docs: Executes GraphQL operation with given server configuration and returns execution result
  (or promise when promise adapter is different from SyncPromiseAdapter)
  
  @return ExecutionResult|Promise
  
  @api