Fix nested serializer

src/documents/serialisers.py

@@ -549,11 +549,17 @@ class TagSerializer(MatchingModelSerializer, OwnedObjectSerializer):
         source="tn_parent",
     )
 
-    def get_children(self, obj):
-        return obj.get_children_pks()
-
+    # children as nested Tag objects
     children = serializers.SerializerMethodField()
 
+    def get_children(self, obj):
+        serializer = self.__class__(
+            obj.get_children(),
+            many=True,
+            context=self.context,
+        )
+        return serializer.data
+
     class Meta:
         model = Tag
         fields = (