The concern that contains `self` or null if `self` is the root of the concern hierarchy

Property definitions

	# The concern that contains `self` or null if `self` is the root of the concern hierarchy
	fun parent_concern: nullable MConcern is abstract

src/model/model_base.nit:116,2--117,50

	# MPackage are always roots of the concerns hierarchy
	redef fun parent_concern do return null

src/model/mpackage.nit:56,2--57,40

	redef fun parent_concern do
		if not is_root then return parent
		return mpackage
	end

src/model/mpackage.nit:174,2--177,4

	redef fun parent_concern do return mgroup

src/model/mmodule.nit:272,2--42