# Returns the visibility as a UML token
	#
	#    assert public_visibility.tpl_class == "+"
	#    assert private_visibility.tpl_class == "-"
	fun tpl_class: Writable do
		if self == private_visibility then
			return "-"
		else if self == protected_visibility then
			return "#"
		else if self == public_visibility then
			return "+"
		else
			return "+"
		end
	end