AttributeError: 'Etcd3Client' object has no attribute 'add_watch_prefix_callback'

Code:
import etcd3
import etcd3.etcdrpc as etcdrpc
import etcd3.exceptions
import etcd3.utils as utils
from etcd3.client import EtcdTokenCallCredentials
etcd = etcd3.client(host='localhost',port=2379)

def watch_callback(event):
print(event)
watch_id = etcd.add_watch_prefix_callback("/foo/", watch_callback)

Message:
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
in
8 def watch_callback(event):
9 print(event)
---> 10 watch_id = etcd.add_watch_prefix_callback("/foo/", watch_callback)

AttributeError: 'Etcd3Client' object has no attribute 'add_watch_prefix_callback'

Start by reproducing the example against the Etcd3Client API and inspect the existing watch-related entry points. Compare the requested add_watch_prefix_callback call with the supported public methods, then verify the expected behavior for watching the /foo/ prefix and receiving events.

Written by the indexing model from the issue text.