public function exists($post_id, string $key = ''): bool
    {
        return (bool) $this->collect($post_id, $key);
    }
public function exists($post_id, string $key = ''): bool
    {
        return (bool) $this->collect($post_id, $key);
    }
public function exists ( $ post_id , string $ key = '' ) : bool { return ( bool ) $ this -> collect ( $ post_id , $ key ) ; }
Meta values exist?

@since 160826 Post meta utils.

@param string|int|null $post_id Post ID; `null` = current.
@param string          $key     Meta key (unprefixed). If empty, checks all metadata.

@return bool True if meta values exist.
Meta values exist?