Multithreaded compression

It was mentioned in the announcement that "Multithreaded compression allows multiple threads to operate in unison on a single file." However, I've been struggling to find any documentation or examples that illustrate this feature. I would greatly appreciate it if someone could share a code snippet or example showing how to utilize this new functionality.
I suspect it is [compress_multi](https://docs.rs/brotli/latest/brotli/enc/multithreading/fn.compress_multi.html#), but the last parameter alloc_per_thread is unclear for me.