code: public function process(ServerRequestInterface $request, HandlerInterface $handler)
      {
          $wrap = class_exists('Zend\Stratigility\Middleware\ErrorHandler');
  
          foreach ($this->stack as $middleware) {
              $middleware = is_string($middleware) ? new $middleware : $middleware;
  
              $this->pipeline->pipe($this->transform($middleware, $wrap));
          }
  
          return $this->pipeline->__invoke($request, $this->response, $handler);
      }
docs: Processes an incoming server request and return a response.
  
  @param  \Psr\Http\Message\ServerRequestInterface      $request
  @param  \Rougin\Slytherin\Middleware\HandlerInterface $handler
  @return \Psr\Http\Message\ResponseInterface