This is used for classifying `time` and `gauge` values.
function makeThresholdsSieve(options, defaults) {

	if (!options) options = {};

	// Pre-apply defaults.
	Object.keys(defaults).forEach(key => options[key] || (options[key] = defaults[key]));

	return (key, overrides) => {
		if (overrides && overrides[key] !== void 0) return overrides[key];
		return options[key];
	}
}