Function resolve_python_relative 

pub fn resolve_python_relative<S: BuildHasher>(
    importer_path: &str,
    target: &str,
    live_paths: &HashSet<String, S>,
) -> Option<String>

Resolve a Python relative-import target (e.g. .foo.bar, ..pkg.x) against the live-at-HEAD path set. Handles both from . import foo and from .foo import bar shapes via the dot-prefix convention. External imports (no leading dot) return None.