function values(o) {
  var ks = Object.keys(o),
      len = ks.length,
      result = new Array(len),
      i;
  for (i = 0; i < len; ++i) {
    result[i] = o[ks[i]];
  }
  return result;
}
Removes a key from this Set. If the key was removed this function returns
`true`. If not, it returns `false`. Takes `O(1)` time.