Error with coros

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I can't find out why this error keeps appearing.

Traceback (most recent call last): File "/home/pi/flasksse_rpi/simple.py", line 12, in <module> from gevent.coros import Semaphore File "/usr/local/lib/python2.7/dist-packages/gevent/builtins.py", line 96, in __import__ result = _import(*args, **kwargs) ImportError: No module named coros

Latest RPI OS: Linux ham-pi 5.10.52-v7+ #1441 SMP Tue Aug 3 18:10:09 BST 2021 armv7l GNU/Linux