Assuming that these functions are not of any Models. Let us assume that inside the "authenticator" module there is a folder called "tools" and inside it a python file called "functions.py" with functions(send_otp, verify_otp).

if you want to use these functions in any other module,:-

First, include the "authenticator" module in depends inside the manifest file.

And import these functions in the needed python file like:-

from odoo.addons.authenticator.tools.functions import send_otp,verify_otp