/**
* Save a key to a file
*
* @param Key|KeyPair $key
* @param string $filename
* @return bool
*/
public static function save($key, string $filename = '') : bool
{
if ($key instanceof KeyPair) {
return self::saveKeyFile($filename, $key->getSecretKey()->getRawKeyMaterial());
}
return self::saveKeyFile($filename, $key->getRawKeyMaterial());
}