readme update

Author: Krzysztof Marciniak

README.rst

@@ -252,6 +252,16 @@ By changing the first line only, a single request fetches all the data. The navi
 
   app = client.v3.apps.get("app-guid", include="space.organization")
 
+.. code-block:: python
+
+  fields = {
+    "space": ["guid,name,relationships.organization"],
+    "space.organization": ["guid","name"]
+  }
+  services_instances = client.v3.service_instances.list(fields=fields)
+
+Relationship object generated by `fields` will contain only attributes returned by the API (eg. name, guid). Please note relationship needs to be explicitly requested, otherwise it will be ignored and child object not created.
+
 Available managers on API V3 are:
 
 - ``apps``