code: public function addGroup($prefix, array $middleware, callable $callback)
      {
          $previousMiddlewareStack = $this->middlewareStack;
          $previousGroupPrefix = $this->currentGroupPrefix;
          $this->currentGroupPrefix = $previousGroupPrefix . $prefix;
          $this->middlewareStack = array_merge($previousMiddlewareStack, $middleware);
          $callback($this);
          $this->currentGroupPrefix = $previousGroupPrefix;
          $this->middlewareStack = $previousMiddlewareStack;
      }
docs: Create a route group with a common prefix.
  
  All routes created in the passed callback will have the given group prefix prepended.
  
  @param string              $prefix      String to be prepended to this route
  @param Middleware|string[] $middleware  Middleware to be added to all routes in this group
  @param callable            $callback    Definition callback