+is set to 1 if the user is a member or 0 if not a member of the group.
+.Fn mbr_check_service_membership
+similarly tests if a given user is a member of a service ACL group. Service
+ACLs are special groups defined with the prefix "com.apple.access_". The
+service is then prefixed (e.g., "afp" would check "com.apple.access_afp").
+There is a special group that grants accessto all services called
+"com.apple.access_all_services".