public function deleteCollections($collections)
    {
        if (is_array($collections)) {
            foreach($collections as $coll) {
                $pos = array_search($coll, $this->collections);
                if($pos !== FALSE) {
                    array_splice($this->collections, $pos, 1);
                }
            }
        } else {
            $pos = array_search($collections, $this->collections);
            if($pos !== FALSE) {
                array_splice($this->collections, $pos, 1);
            }
        }
        return $this;
    }