Python's cProfiler: method 'pop' of 'list' objects

Question

I am trying to profile a python script I have. I run it like this:

$ python -m cProfile -o out.profile script.py

It runs well, I get a file called out.profile with profiling information, but I see that the biggest influencer in execution time is this:

~:0(<method 'pop' of 'list' objects>)

With 77% of the execution time. Here is a chart I got with snakeviz.

So, my question is:

What part of the python API might be using 'pop' method of 'list' object? Because I am not calling pop explicitly anywhere in my script.

Update: This is the CALL STACK I have on that method: