This method is only available on newer versions.
The first available version (v2_6_3) is shown here.
chown(user, group, list, noop: nil, verbose: nil)
private
Changes owner and group on the named files (in list) to the user
user and the group group. user and
group may be an ID (Integer/String) or
a name (String). If user or
group is nil, this method does not change the attribute.