code: function mapValues (obj, fn) {
    return Object.keys(obj).reduce(function (subresult, key) {
      subresult[key] = fn(obj[key], key)
      return subresult
    }, {})
  }
docs: Apply a function to each value of an object and return the result
  @param {object<any>} obj
  @param {function(any, string): any} fn
  @returns {object<any>}
  @private