code: function template(strings, ...keys) {
    return function(...values) {
      let dict = values[values.length - 1] || {};
      let result = [strings[0]];
      keys.forEach(function(key, i) {
        let value = isInteger(key) ? values[key] : dict[key];
        result.push(value, strings[i + 1]);
      });
      return result.join('');
    };
  }
docs: A helper function to form URL from the template