chore: docstring for get_public_model_scoped_queryset(...)

chord_metadata_service/discovery/utils.py

@@ -234,6 +234,19 @@ def get_discovery_field_set_permissions(
 
 
 def get_public_model_scoped_queryset(scope: ValidatedDiscoveryScope, mn: PublicModelName) -> QuerySet:
+    """
+    Discovery models can be scoped to either a project or dataset; for downstream filtering, we need to pre-scope the
+    model queryset to the project/dataset being queried.
+
+    Since downstream filtering may be applied to (possibly deeply)nested fields/models (e.g., biosamples, experiments),
+    we use `.distinct()` instead of `.all()`. Otherwise, there may be multiple instances of the same top-level object
+    (individual especially, which has this deep nesting) for each nested instance, for example, in the case of multiple
+    experiments for a biosample for an individual.
+
+    :param scope: The scope to filter the queryset to.
+    :param mn: The discovery/"public" model name for
+    """
+
     filter_scope: PublicScopeFilterKeys
     if scope.dataset_id:
         filter_scope = "dataset"