Function percent_encode_set 

pub fn percent_encode_set(s: &str, set: &'static AsciiSet) -> String

Percent-encode s with a caller-supplied AsciiSet.

For the common case prefer percent_encode. Reach for this only when a backend needs a different escape set — build one from the re-exported CONTROLS / NON_ALPHANUMERIC + AsciiSet::add/AsciiSet::remove.