The standard library quickstring_red_black_set package implements quickstring__premicrothread-keyed sets.
The quickstring_red_black_set package implements the Set API via red_black_set_g from src/lib/src/red-black-set-g.pkg.
The quickstring_red_black_set package source code is in src/lib/src/quickstring-red-black-set.pkg.
The above information is manually maintained and may contain errors.
Set?