# Retrieve the associated AST node of a mentity.
	# This method is used to associate model entity with syntactic entities.
	#
	# If the mentity is not associated with a node, returns null.
	# This is always the case for MPackage, Mgroup, MClass and MProperty.
	# MModule, MClassDef and MPropDef can also have no node associated
	# (like fictive modules of generated attributes/methods).
	fun mentity2node(mentity: MEntity): nullable ANode
	do
		if mentity isa MModule then
			return mmodule2node(mentity)
		else if mentity isa MClassDef then
			return mclassdef2node(mentity)
		else if mentity isa MPropDef then
			return mpropdef2node(mentity)
		end
		return null
	end