Need to add additional functionality to nova service and would like to know if there is any supporting sight or document.

I have this question because when i try doing below steps i got the below errors and am clueless on how to set the TRANSPORT variable

from nova.api.openstack.compute.servers import Controller c= Controller() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/dist-packages/nova/api/openstack/compute/servers.py", line 119, in __init__ self.compute_api = compute.API() File "/usr/lib/python2.7/dist-packages/nova/compute/__init__.py", line 39, in API return importutils.import_object(class_name, args, *kwargs) File "/usr/lib/python2.7/dist-packages/oslo_utils/importutils.py", line 38, in import_object return import_class(import_str)(args, *kwargs) File "/usr/lib/python2.7/dist-packages/nova/compute/api.py", line 277, in __init__ skip_policy_check=skip_policy_check) File "/usr/lib/python2.7/dist-packages/nova/network/__init__.py", line 35, in API return cls(skip_policy_check=skip_policy_check) File "/usr/lib/python2.7/dist-packages/nova/network/api.py", line 70, in __init__ self.network_rpcapi = network_rpcapi.NetworkAPI() File "/usr/lib/python2.7/dist-packages/nova/network/rpcapi.py", line 123, in __init__ self.client = rpc.get_client(target, version_cap, serializer) File "/usr/lib/python2.7/dist-packages/nova/rpc.py", line 130, in get_client assert TRANSPORT is not None AssertionError

Thanks in advance, Chandralekha