Updating comment

greg/api/serializers/person.py

@@ -39,17 +39,19 @@ class PersonIdentitySerializer(serializers.ModelSerializer):
         fields = "__all__"
 
     def is_duplicate(self, identity_type: str, value: str) -> bool:
-        # If the type is other then it is allowed that two entries are the same, since
-        # the text may be some generic text added by the sponsor
+        # Guests may be verified using another unrecognised identification method,
+        # which the sponsor is required to elaborate in the value column.
+        # In this case we cannot assume the union of the identity type and
+        # the value to be unique across all records.
         if identity_type == PersonIdentity.IdentityType.OTHER:
             return False
 
         # If the type is a specific ID type, then duplicates are not expected
         return (
-            len(
-                PersonIdentity.objects.filter(type__like=identity_type).filter(
-                    value__like=value
+                len(
+                    PersonIdentity.objects.filter(type__like=identity_type).filter(
+                        value__like=value
+                    )
                 )
-            )
-            > 0
+                > 0
         )