code: protected function request($argument, ServerRequestInterface $request = null)
      {
          $instanceof = $argument instanceof ServerRequestInterface;
  
          $instanceof === true && $argument = $request ?: $argument;
  
          return $argument;
      }
docs: Returns the manipulated ServerRequest (from middleware) to an argument.
  
  @param  mixed                                         $argument
  @param  \Psr\Http\Message\ServerRequestInterface|null $request
  @return mixed