Filter based on whether an update (of any sort) is available.

def queryset(self, request, queryset):
        """Filter based on whether an update (of any sort) is available."""
        if self.value() == '-1':
            return queryset.filter(latest_version__isnull=True)
        elif self.value() == '0':
            return (
                queryset
                .filter(
                    current_version__isnull=False,
                    latest_version__isnull=False,
                    latest_version=F('current_version')
                )
            )
        elif self.value() == '1':
            return (
                queryset
                .filter(
                    current_version__isnull=False,
                    latest_version__isnull=False
                ).exclude(
                    latest_version=F('current_version')
                )
            )
        else:
            return queryset