LJ::get_reluser_id — for reluser2, numbers 1 - 31999 are reserved for livejournal stuff, whereas numbers 32000-65535 are used for local sites. if you wish to add your own hooks to this, you should define a hook "get_reluser_id" in ljlib-local.pl no reluser2 types can be a single character, those are reserved for the reluser table so we don't have namespace problems.
type. the name of the type you're trying to access, e.g. "hide_comm_assoc"
id of type, 0 means it's not a reluser2 type