Which openCV tools can measure line thickness? Which part of the library does this apply to?

Question

Python

I am currently learning OpenCV in python. I settled on the contours, namely, finding numbers on a white background for some reason. Now I came up with a new task - to recognize the largest digit in the image in terms of thickness.
I was able to recognize all the numbers themselves by converting the picture to bw format using threshold transformations. However, then I fell into a stupor, because I don’t understand how to explain to the program that I want to find the symbol by the thickness and not by the size or the area occupied. I reviewed different sections, namely: morphological operations (it was said that they are related to working with the shape of objects, but then I realized that this work with the shape refers more to removing any inaccuracies, noise, irregularities in the image, leaving only a frame with which it will be more convenient to work further. Is this true?), Contours (functions contourArea, arcLength. However, with them the program displayed only the largest or smallest number precisely in size, and not in thickness),
This is where my ideas on how to calculate this damned thickness ended. I would like to ask you, if possible, to tell me which sections in opencv I exactly need to look at to solve the problem, giving this some kind of tip, and then I will write a normal algorithm. Or, if this task does not apply to OpenCV, then say that I need to look outside of it. And if it requires some kind of math, what kind? I will be very grateful.