# Collect all virtual types introduced in `self`
	fun collect_intro_vts(filter: nullable ModelFilter): Set[MVirtualTypeProp] do
		var res = new HashSet[MVirtualTypeProp]
		for mgroup in mgroups do
			for mmodule in collect_all_mmodules(filter) do
				res.add_all mmodule.collect_intro_vts(filter)
			end
		end
		return res
	end