I find that the best approach is to talk to them first, explain your use case, ask them how to solve the problem. Most of the time you will either be welcomed

I find that the best approach is to talk to them first, explain your use case, ask them how to solve the problem. Most of the time you will either be welcomed for your proper obsequence, or find out that there's a jealous guardian of that code and no matter what you do it won't alleviate that tension anyway.