This article[0] and a clarifying comment[1] answer the question for JS. I think it's the same for Python. Apparently your model (which was mine, too) is out of date!
I think the argument is that there are multiple judicial philosophies that can be chosen from, and you can generally predict what outcomes will result from following a philosophy consistently over time, so a justice chooses the philosophy that results in the outcomes they want. And therefore they could have chosen their philosophy for partisan outcome-based reasons, so consistently following it is no defense to accusations of partisanship.
I would call it a duty more than a debt. I feel that I have a duty to look after my elders, but I do not think my children owe me a debt for conceiving them or for performing my own duty to take care of them.
[0] https://hacks.mozilla.org/2015/05/es6-in-depth-generators/
[1] https://hacks.mozilla.org/2015/05/es6-in-depth-generators/#c...