public function keys()
    {
        $map = new Map;
        foreach (array_keys($this->array) as $hash) {
            $map[] = $this->hash_to_key($hash);
        }
        return $map;
    }
public function keys()
    {
        $map = new Map;
        foreach (array_keys($this->array) as $hash) {
            $map[] = $this->hash_to_key($hash);
        }
        return $map;
    }
public function keys ( ) { $ map = new Map ; foreach ( array_keys ( $ this -> array ) as $ hash ) { $ map [ ] = $ this -> hash_to_key ( $ hash ) ; } return $ map ; }
Get the keys of this map as a new map.

@return new Map
@api
@since 1.0.5
Get the keys of this map as a new map .