code: def nova_client(self):
          
          if not self._client:
              self._client = self._get_nova_client()
          return self._client
docs: Each of the OpenStack client libraries (i.e. the ``python-*client``
          projects that live under https://github.com/openstack/) has its own way
          of connecting to the identity service (keystone).
  
          The object returned here is a :class:`novaclient.v1_1.client.Client`.