code: function arity(length, nativeFunction) {
    return (new Function('f', 'return function (' + Array.apply(null, Array(length)).map(function (_, index) {
      return '_' + index;
    }).join(',') + ') { return f.apply(this, arguments); }'))(nativeFunction);
  }
docs: eslint-disable-next-line no-unused-vars