# Collect all MPropDefs in `self`
	fun collect_mpropdefs(filter: nullable ModelFilter): HashSet[MPropDef] do
		var res = new HashSet[MPropDef]
		for mproperty in collect_mproperties(filter) do
			for mpropdef in mproperty.mpropdefs do
				if filter == null or filter.accept_mentity(mpropdef) then res.add mpropdef
			end
		end
		return res
	end