def format_lockfile(self, repository: LockedRepository, groups: Iterable[str] | None, strategy: set[str]) -> None:
        """Format lock file from a dict of resolved candidates, a mapping of dependencies
        and a collection of package summaries.
        """
Format lock file from a dict of resolved candidates, a mapping of dependencies
        and a collection of package summaries.
        
src/pdm/project/lockfile/base.py