def METHOD_NAME(
    cls,
    config: Dict[str, Any],
    key: str,
    defaults: Optional[Dict[str, float]] = None,
) -> "RatelimitSettings":
    """Parse config[key] as a new-style rate limiter config.
    The key may refer to a nested dictionary using a full stop (.) to separate
    each nested key. For example, use the key "a.b.c" to parse the following:
    a:
      b:
        c:
          per_second: 10
          burst_count: 200
    If this lookup fails, we'll fallback to the defaults.
    """
    defaults = defaults or {"per_second": 0.17, "burst_count": 3.0}
    rl_config = config
    for part in key.split("."):
        rl_config = rl_config.get(part, {})
    # By this point we should have hit the rate limiter parameters.
    # We don't actually check this though!
    rl_config = cast(Dict[str, float], rl_config)
    return cls(
        key=key,
        per_second=rl_config.get("per_second", defaults["per_second"]),
        burst_count=int(rl_config.get("burst_count", defaults["burst_count"])),
    )