How to systematically debug nested dict JSON serialization errors in Python?

[Jacob.P]

I'm an intermediate Python developer working on a data processing script that's throwing a persistent and cryptic error when I try to serialize a complex nested dictionary to JSON. I've used print statements and basic pdb, but the traceback points to a library function deep in the call stack, and I'm struggling to isolate whether the issue is in my data structure, a custom encoder I wrote, or something else entirely. For more experienced developers, what's your systematic approach to Python debugging in a situation like this? Are there specific tools or techniques, like better use of the logging module, conditional breakpoints in an IDE, or visualizing the object state, that you find indispensable for untangling these kinds of nested data problems? How do you effectively narrow down the root cause when the error manifests far from where the bug actually lives?