# Is this attribute nullable for sure?
	#
	# This mean that its introduction is declarred with a nullable static type
	# since attributes are invariant this will work on most cases
	# attributes with static type anchored with a virtual type are not "nullable for-sure"
	# because this type can be redefined in subclasses
	private fun is_nullable: Bool do return intro.static_mtype isa MNullableType