public function keys()
    {
        return $this->create(array_keys($this->toArray()))->map(
            function ($key) {
                return new String($key);
            }
        );
    }
public function keys()
    {
        return $this->create(array_keys($this->toArray()))->map(
            function ($key) {
                return new String($key);
            }
        );
    }
public function keys ( ) { return $ this -> create ( array_keys ( $ this -> toArray ( ) ) ) -> map ( function ( $ key ) { return new String ( $ key ) ; } ) ; }
Get the array keys

@return Hash[String] containing the keys
Get the array keys