[racket] Using the profiler effectively?

> JFYI, I have revised the documentation, which had a bunch of pretty
> bad points.  But that's probably not what you want; hopefully my
> earlier reply was helpful, and more hopefully someone will write up a
> "guide" part for the docs, to similarly clarify things.


Apologies: I'm still very confused, as usual.  The documentation says
about the render function that I can save the profile for future
rendering.  But I can't easily save it to disk because the profile
structure is opaque.  What does the documentation mean here?