redef var class_inheritance_metamodel is lazy do
		var engine = new JsonDeserializer(class_inheritance_metamodel_json.to_s)
		engine.check_subtypes = false
		engine.whitelist.add_all(
			["String", "POSet[String]", "POSetElement[String]",
			 "HashSet[String]", "HashMap[String, POSetElement[String]]"])

		var poset = engine.deserialize
		if engine.errors.not_empty then
			print_error "Deserialization errors in class_inheritance_metamodel:"
			print_error engine.errors.join("\n* ")
			return new POSet[String]
		end

		if poset isa POSet[String] then return poset
		return new POSet[String]
	end