Can't put dicts in a set

src/cal_tools/calcat_interface2.py

@@ -448,10 +448,10 @@ class CalibrationData(Mapping):
         res = client.get("calibration_constant_versions", params)
 
         d = {}
-        pdus = set()
+        pdus = []
 
         for ccv in res:
-            pdus.add(ccv["physical_detector_unit"])
+            pdus.append(ccv["physical_detector_unit"])
             cal_type = calibration_name(ccv["calibration_constant"]["calibration_id"])
             aggr = ccv["physical_detector_unit"]["karabo_da"]
             d.setdefault(cal_type, {})[aggr] = SingleConstantVersion.from_response(ccv)