docs: function(obj, multi) {
      var result = {};
      multi = multi === true;
      forEachProperty(obj, function(val, key) {
        if (hasOwn(result, val) && multi) {
          result[val].push(key);
        } else if (multi) {
          result[val] = [key];
        } else {
          result[val] = key;
        }
      });
      return result;
    }