Local variable 'bkey_hash' referenced before assignment

Dash Python
6

Now it is showing import errors:

File “c:\Users\EliasPai\DocumentsRIKA\DashRika\app.py”, line 29, in
from dash_extensions.callback import CallbackCache, Trigger
ModuleNotFoundError: No module named ‘dash_extensions.callback’

In the documentation I didn’t find this term.

I am basing this example on the link.