PR #3870 failed to speed up Leo's beautifier but did speed up Leo's beautification scripts. As a result, I see no reason to transliterate leoTokens.py into Rust.
I now know what programming in Rust feels like. Rust has its place, but I have no further interest in it :-) Python allows me to concentrate on ideas, and that's all I care about.
Onward to other adventures!
Edward