code: public function getIsStorageExistAsync(Requests\GetIsStorageExistRequest $request) 
      {
          return $this->getIsStorageExistAsyncWithHttpInfo($request)
              ->then(
                  function ($response) {
                      return $response[0];
                  }
              );
      }
docs: /*
  Operation getIsStorageExistAsync
  
  Check if storage exists
  
  @param Requests\GetIsStorageExistRequest $request is a request object for operation
  
  @throws \InvalidArgumentException
  @return \GuzzleHttp\Promise\PromiseInterface