How to use the handprint.credentials.base.Credentials.creds_dir function in handprint

def save_credentials(self, service, supplied_file):
        if not path.isdir(Credentials.creds_dir):
            if __debug__: log('creating credentials dir: {}.', Credentials.creds_dir)
            make_dir(Credentials.creds_dir)
        dest_file = path.join(Credentials.creds_dir, credentials_filename(service))
        copy_file(supplied_file, dest_file)

def credentials_dir(self):
        return Credentials.creds_dir

def save_credentials(self, service, supplied_file):
        if not path.isdir(Credentials.creds_dir):
            if __debug__: log('creating credentials dir: {}.', Credentials.creds_dir)
            make_dir(Credentials.creds_dir)
        dest_file = path.join(Credentials.creds_dir, credentials_filename(service))
        copy_file(supplied_file, dest_file)