ModuleNotFoundError only on system but not on Colab

The following error is not occurring when I run my code on Colab. And I am facing this error when I try to run on my system

Traceback (most recent call last):
  File "program.py", line 224, in <module>
    import infun
ModuleNotFoundError: No module named 'infun'

I changed to the directory in which my infun present i.e., infunner at the start of my program program.py

import os
os.chdir('infunner')

And I find no difference in paths of files provided for program execution in both Colab and on my system.

What is the reason for this error?

The file structure is as follows

├───program.py
├───infunner
│   ├───infun
│   ...
...