wp-admin/includes/class-wp-filesystem-ftpext.php:327Gets the file's group.
$filestringstring|false public function group( $file ) { $dir = $this->dirlist( $file ); return $dir[ $file ]['group']; }Introduced in 2.5.0. One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
string|false to string|int<1,.verified against sourcesrc/wp-admin/includes/class-wp-filesystem-ftpext.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.