Editing WoW:API CollapseTrainerSkillLine

{{wowapi}}
Collapses a header, hiding all spells below it.

 CollapseTrainerSkillLine(id);

----
;''Arguments''

:; id : Index of the trainer service header to collapse (if the supplied index is not a header, an error is produced). Note that indices are affected by the trainer filter. (See [[API_GetTrainerServiceTypeFilter|GetTrainerServiceTypeFilter]] and [[API_SetTrainerServiceTypeFilter|SetTrainerServiceTypeFilter]].)

----
;''Example''

Collapses all trainer headers.
 local i, category;
 for i=1,GetNumTrainerServices() do
  _ , _, category = GetTrainerServiceInfo(i);
  if (category == nil) then
   break; -- GetNumTrainerServices() does not check if you're talking to a trainer or not.
  end
  if (category == "header") then
   CollapseTrainerSkillLine(i);
  end
 end