Improve API docs

arkindex/training/serializers.py

@@ -542,6 +542,10 @@ class DatasetSerializer(serializers.ModelSerializer):
     set_elements = DatasetSetsCountField(
         help_text="Distribution of elements in sets. This value is set to null when listing multiple datasets.",
     )
+    unique_elements = serializers.BooleanField(
+        default=True,
+        help_text="Ensures that an element is only present in a single set at a time.",
+    )
 
     def validate_state(self, state):
         """