/**
* Get a flattened array of the items in the collection.
*
* @param int $depth
* @return static
*/
public function flatten($depth = INF)
{
return new static(Arr::flatten($this->items, $depth));
}
/**
* Flatten a multi-dimensional array into a single level.
*
* @param array $array
* @param int $depth
* @return array
*/
function array_flatten($array, $depth = INF)
{
return Arr::flatten($array, $depth);
}