Symfony\Component\Routing\RouteCollection::setParent PHP Method

    private function setParent(RouteCollection $parent)
    {
        $this->parent = $parent;
    }

 /**
  * Adds a route collection to the current set of routes (at the end of the current set).
  *
  * @param RouteCollection $collection A RouteCollection instance
  * @param string          $prefix     An optional prefix to add before each pattern of the route collection
  *
  * @api
  */
 public function addCollection(RouteCollection $collection, $prefix = '')
 {
     $collection->setParent($this);
     $collection->addPrefix($prefix);
     // remove all routes with the same name in all existing collections
     foreach (array_keys($collection->all()) as $name) {
         $this->remove($name);
     }
     $this->routes[] = $collection;
 }