add providerId attr to LabsLink link element

biodblinks/lablinks/serializer.py

@@ -43,7 +43,7 @@ class Serializer(BaseSerializer):
             obj_pk = obj.pk
             if obj_pk is not None:
                 attrs["pk"] = str(obj_pk)
-        self.xml.startElement("link", {})
+        self.xml.startElement("link", {'providerId': settings.LABLINKS_PROVIDER_ID})
         self.xml.startElement("resource", {})
         self.indent(3)
         self.xml.startElement("title", {})