Function is_prerelease 

pub fn is_prerelease(version: &str) -> bool

Whether version has a semver 2.0.0 prerelease component.

Pub requires published versions to be strict semver, so any hyphen preceding optional +build metadata reliably marks a prerelease — unlike deps-core’s default keyword-based heuristic, this also catches conventions not in its fixed list, e.g. Dart’s nullsafety preview tag (2.10.0-nullsafety.1) (#322).