DNS Documentation inconcistencies #1603

The DNS documentation requires updating.

import time
from gcloud import dns
client = dns.Client(project='PROJECT_ID')
zone = client.zone('acme-co')
record = dns.ResourceRecord(name='www.example.com', type='CNAME')
change = zone.change_request(additions=[record])
change.begin() # API request
while change.status != 'done':
... print('Waiting for change to complete')
... time.sleep(60) # or whatever interval is appropriate
... change.reload() # API request`

E.g. the method zone.change_request() is not available and the change set methods have replaced it.