/**
 * Get single value from key in instance map based on $selector::$key
 *
 * @access private
 *
 * @param {String}  $key    - breakpoint key to pass to instance method
 * @param {ArgList} $values - list of keys to fetch value from
 *
 * @return {String | False}
 */
@function flint-get-instance-value($key, $values...) {
	@return flint-map-fetch($flint__instances, flint-has-family-instance($key), $values...);
}