WP_Filesystem_SSH2::group( string $file )

	public function group($file) {
		$gid = @filegroup( $this->sftp_path( $file ) );
		if ( ! $gid )
			return false;
		if ( ! function_exists('posix_getgrgid') )
			return $gid;
		$grouparray = posix_getgrgid( $gid );
		if ( ! $grouparray ) {
			return false;
		}
		return $grouparray['name'];
	}