code: public static function has(Item $parent, Item $child)
      {
          $key = md5($parent->systemId . "." . $child->systemId);
  
          return isset(self::$_relationships[$key]);
      }
docs: [[@doctodo method_description:has]].
  
  @param cascade\components\types\Item $parent [[@doctodo param_description:parent]]
  @param cascade\components\types\Item $child  [[@doctodo param_description:child]]
  
  @return [[@doctodo return_type:has]] [[@doctodo return_description:has]]