This is not perfect as mypy at least doesn't consider e.g. subclasses of
the property decorator class to behave the same way, but it's as good as
we can get without introducing a mypy plugin.
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
Change-Id: Ia0c4110218ce8a48c3ec5e720f07e45fc2b831bf
7abbf7a443