.async syntax error while installing google assistant sdk

Question

I am using python 3.7.3 version and i am getting an syntax error.

'''' (env) pi@raspberrypi: $ googlesamples-assistant-pushtotalk-project-id ***** --device-model-id ********

Traceback (most recent call last):

File "/home/pi/env/bin/googtesamples assistant-pushtotalk", line 5, in from googlesamples.assistant.grpc.pushtotalk import main

File "/home/pi/env/Lib/python3.7/site-packages/googlesamples/assistant/grpc/pushtotalk.py", line 29, in

from tenacity import retry, stop_after_attempt, retry if exception

File "/home/pi/env/lib/python3.7/site-packages/tenacity/ init__.py", line 292

from tenacity.async import AsyncRetrying

SyntaxError: invalid syntax ''''