Avoid setting the slot duration at import

Addresses #14 (closed)

AKModel/views/ak.py

@@ -61,7 +61,7 @@ class AKJSONExportView(AdminViewMixin, FilterByEventSlugMixin, ListView):
 
     def _test_ak_fixed_in_slot(self, ak_id, slot: Availability, ak_fixed: dict) -> bool:
         """Test if AK defined by `ak_id` is fixed to happen during slot."""
-        if not ak_id in ak_fixed:
+        if ak_id not in ak_fixed:
             return False
 
         fixed_slot = Availability(self.event, start=ak_fixed[ak_id].start, end=ak_fixed[ak_id].end)