code: public function getCurrentItem($menu)
      {
          if (null === $this->matcher) {
              throw new \BadMethodCallException('The matcher must be set to get the current item of a menu');
          }
  
          $menu = $this->castMenu($menu);
  
          return $this->retrieveCurrentItem($menu);
      }
docs: Returns the current item of a menu.
  
  @param ItemInterface|array|string $menu
  
  @return ItemInterface|null