def METHOD_NAME():
    """
    Fetch flattened ECS fields based on ECS 1.6.0 spec
    The result of this function is cached
    """
    url = "https://raw.githubusercontent.com/elastic/ecs/v1.6.0/generated/ecs/ecs_flat.yml"
    resp = requests.get(url)
    if resp.status_code != 200:
        raise ValueError(resp.content)
    return yaml.load(resp.content, Loader=yaml.FullLoader)