Why is my function is showing not defined in python?

In my pycharm have 2 files, main.py and lab3.py in my lab3.py file i have a code like this

https://i.stack.imgur.com/tRCfU.png

it's showing me error

 Traceback (most recent call last):
  File "/Users/mavi/PycharmProjects/Lab3/lab3.py", line 18, in <module>
    if annual_income >= 50000:
NameError: name 'annual_income' is not defined

in my main.py file i wrote this

https://i.stack.imgur.com/A89a8.png

this is what i'm hoping as a result but I can't proceed because of the errors.

https://i.stack.imgur.com/vRzqF.png

i'm a beginner and this is confusing for me, what am I doing wrong and how will I fix the error. I tried other ways and it showed me more errors. Thank you for the help in advance!