create index query returns nonetype object

Added the following method to sdk_client.py file:
https://github.com/couchbase/testrunner/blob/master/lib/sdk_client.py

def single_result(self,query):
result = self.cb.n1ql_query(query).get_single_result()
print result
return result

Initialized the client in my query code and tried to call single_result function as:
host = self.master.ip
self.create_users()
self.assign_role(roles=[

{'id': 'default', 'name': 'default', 'roles': 'admin' }

])
client = SDKClient(hosts = [host],bucket = 'default')
client._createConn()
result = client.single_result(query)
print result

The result is a Nonetype object for all create index queries.