AttributeError: module 'aiosip' has no attribute 'WS'

[divinj]

I installed aiosip using pip3.
I am trying to run https://github.com/Eyepea/aiosip/blob/master/examples/call/client.py

Running into:
DEBUG:asyncio:Using selector: KqueueSelector
Traceback (most recent call last):
File "aiosip-test.py", line 83, in
main()
File "aiosip-test.py", line 70, in main
loop.run_until_complete(start(app, aiosip.UDP, args.duration))
File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py", line 583, in run_until_complete
return future.result()
File "aiosip-test.py", line 45, in start
if protocol is aiosip.WS:
AttributeError: module 'aiosip' has no attribute 'WS'

Any idea what is causing this?