Sculpin\Contrib\ProxySourceCollection\ProxySourceItem::id PHP Method

    public function id()
    {
        return $this->sourceId();
    }

 public function setNextItem(ProxySourceItem $item = null)
 {
     $lastNextItem = $this->nextItem;
     $this->nextItem = $item;
     if ($lastNextItem) {
         // We did have a item before...
         if (!$item || $item->id() !== $lastNextItem->id()) {
             // But we no longer have a item or the item we
             // were given does not have the same ID as the
             // last one we had...
             $this->reprocess();
         }
     } elseif ($item) {
         // We didn't have a item before but we do now...
         $this->reprocess();
     }
 }