def METHOD_NAME(self, artifact:str) -> str:
    """Creates a detached ASCII-armored signature for an artifact."""
    # We expect the PLZ_GPG_KEY and GPG_PASSWORD env vars to be set.
    out = artifact + '.asc'
    if FLAGS.dry_run:
        log.info('Would sign %s into %s', artifact, out)
    else:
        subprocess.check_call([FLAGS.signer, 'pgp', '-o', out, '-i', artifact])
    return out