What tools help debug NoneType unsubscriptable errors in Python data pipelines?

[LoganSP]

I'm a junior developer working on a Python data pipeline that keeps failing with a cryptic error about a NoneType object being unsubscriptable, but the traceback points to a line deep inside a library module, not my own code. I've been using print statements for Python debugging, but it's becoming inefficient as the script grows. For more experienced developers, what systematic approach or tools do you recommend for isolating the root cause when the error originates from a third-party library or complex data flow? I'm particularly interested in learning how to effectively use a proper debugger to step through the execution and inspect the state of my data structures at the point of failure.