def METHOD_NAME(
    endpoint_env_var='SECRETS_SERVER_ENDPOINT',
    concourse_secret_env_var='SECRETS_SERVER_CONCOURSE_CFG_NAME',
    cache_file='SECRETS_SERVER_CACHE'
):
    if cache_file not in os.environ:
        if not all(map(
                    lambda e: e in os.environ,
                    (endpoint_env_var, concourse_secret_env_var)
                    )):
            raise ValueError('the following environment variables must be defined: {v}'.format(
                v=', '.join((endpoint_env_var, concourse_secret_env_var))
            ))
    cache_file = os.environ.get(cache_file, None)
    secret = get_secret_cfg_from_env_if_available()
    return SecretsServerClient(
        endpoint_url=os.environ.get(endpoint_env_var),
        concourse_secret_name=os.environ.get(concourse_secret_env_var),
        cache_file=cache_file,
        secret=secret,
    )