I was meaning that the user would intend to compute the max of some input and time.

I think the problem with the forced two-argument approach is that it really complicates our simple example/teaching scripts.  Even if we don't do it with lambda functions, it would still add a lot of overhead.

I guess an optional n_args parameter would be alright.  You could leave the current introspection stuff in there in the case that they don't specify anything, then at line 55-56 below just change the error message to something like "Could not figure out output function arguments, please specify the n_args parameter in node constructor".