Make discoverable placeholder container writer methods

[zslayton]

          So, I had an idea since this note isn't very discoverable by users. We could add a no-op implementation of `write_list`, etc. that has an empty type as one of the function arguments. It's not callable because you can't create an argument to pass to it, but it can hold this note directing users to the workaround. Then, once this limitation is fixed, we can change the argument type of the function to the correct argument type.

Originally posted by @popematt in #686 (comment)