code: def queryset(self, request, queryset):
  		
  		if self.value() is None:
  			return queryset.all()
  		else:
  			return queryset.filter(subscriptions__status=self.value()).distinct()
docs: Return the filtered queryset based on the value provided in the query string.
  
  		source: https://docs.djangoproject.com/en/1.10/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_filter