Gc\Document\Collection::load PHP Method

    public function load($parentId = null)
    {
        if ($parentId !== null) {
            $this->setData('parent_id', $parentId);
            $this->setDocuments();
        }
        return $this;
    }

 /**
  * Returns documents
  * $data can be mixed
  * if data is an array, return all documents
  * if data is numeric, return all documents with parent_id equal to $data
  * if data is string, return all documents with parent's url key equal to $data
  *
  * @param mixed $data Data
  *
  * @return array \Gc\Document\Model
  */
 public function __invoke($data = null)
 {
     $elements = array();
     $documents = new DocumentCollection();
     if (empty($data)) {
         $elements = $documents->load(0)->getDocuments();
     } else {
         if (is_numeric($data)) {
             $elements = $documents->load($data)->getDocuments();
         } elseif (is_string($data)) {
             $document = DocumentModel::fromUrlKey($data);
             $elements = $document->getChildren();
         } elseif (is_array($data)) {
             foreach ($data as $documentId) {
                 if (empty($documentId)) {
                     continue;
                 }
                 $document = $this->getView()->document($documentId);
                 if (!empty($document)) {
                     $elements[] = $document;
                 }
             }
         }
     }
     return $elements;
 }