# Collect intro abstract mmethodDef
	fun collect_abstract_methods(filter: ModelFilter): Set[MMethodDef] do
		var set = new HashSet[MMethodDef]
		var mpropdefs = collect_intro_mpropdefs(filter)
		for mpropdef in mpropdefs do
			if mpropdef isa MMethodDef then
				if mpropdef.is_abstract then set.add(mpropdef)
			end
		end
		return set
	end