/**
 * Returns a number between 1 and 0, where 1 means they are exactly the same and 0 means no common subsequences.
 * If either string is not a string, returns NaN
 * @param {string} s1
 * @param {string} s2
 * @returns {number}
 */
export default function metriclcs(s1: string, s2: string): number;