Remove pincushion lens distortion in Python

I have the following image which is computer generated

It is fed as an input to an optical experiment results in the following image:

As you can tell the image has a double concave effect due to the lens system being used.

I need to be able to restore the image without distortion and compare it with the original image. I'm new to image processing and I came across two useful python packages:

https://pypi.org/project/defisheye/

The defisheye was quite straight forward for me to use (script below) but i'm not able to achieve the optimal result so far.

from defisheye import Defisheye

dtype = 'linear'
format = 'fullframe'
fov = 11
pfov = 10

img = "input_distorted.jpg"
img_out = "input_distorted_corrected.jpg"

obj = Defisheye(img, dtype=dtype, format=format, fov=fov, pfov=pfov)

# To save image locally 
obj.convert(outfile=img_out)

Seconly from opencv: https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html The camera calibration tutorial is way out of my knowledge. If someone could assure me if that's the way to go i can start digging in deeper. Really appreciate any suggestions.

from Remove pincushion lens distortion in Python