# Collect all class definitions introduced in `self`
	fun collect_intro_mclassdefs(filter: nullable ModelFilter): Set[MClassDef] do
		var res = new HashSet[MClassDef]
		for mclassdef in mclassdefs do
			if not mclassdef.is_intro then continue
			if filter == null or filter.accept_mentity(mclassdef) then res.add mclassdef
		end
		return res
	end