code: function mapValues (obj, fn) {
    return Object.keys(obj).reduce(function (res, key) {
      res[key] = fn(obj[key], key, obj)
      return res
    }, {})
  }
docs: Create a new object with the same keys and values mapped using provided fn.
  
  This is a simplified version of lodash.mapValues.
  
  @param {Object} obj The source object.
  @param {Function} fn The function to map the object's values.
  @returns {Object} The mapped object.