[logback-user] How does the custom ContextSelector work?

I have posed this question on stackoverflow: http://stackoverflow.com/questions/23088466/what-is-the-point-of-logbacks-cu... Unfortunately with no replies. My question is essentially: How can I get a specific context by name if there is no ".getContext(name)" method? Isn't that the point of the whole custom context selection mechanism? But on what grounds can I select a context if I can't pass a string (or anything else) to ".getContext()"? Thank you for your help in advance.