code: public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
      {
          $middleware = $this->container->get($this->middleware);
  
          if ($middleware instanceof MiddlewareInterface) {
  
              return $middleware->process($request, $handler);
  
          }
  
          throw new ContainedMiddlewareTypeException($this->middleware, $middleware);
      }
docs: Get a middleware from the container then proxy its ->process() method.
  
  @param \Psr\Http\Message\ServerRequestInterface  $request
  @param \Psr\Http\Server\RequestHandlerInterface  $handler
  @return \Psr\Http\Message\ResponseInterface
  @throws \Ellipse\Middleware\Exceptions\ContainedMiddlewareTypeException