I sometimes use an ellipsis statement in example code to indicate "stuff goes here" and "this is not executable". In the example that branch of the code is not expected to be executed.

I sometimes use an ellipsis in code I am writing to say "work needed here" and to give me a sharp whack upside of the head if that branch of the code does get executed. In a test environment exception handling can detect unimplemented code that way and report it so appropriate tests can be written that will fail with a useful message until the code is implemented.