code: func (obj *object) Map(f func(*Term, *Term) (*Term, *Term, error)) (Object, error) {
  	cpy := newobject(obj.Len())
  	err := obj.Iter(func(k, v *Term) error {
  		var err error
  		k, v, err = f(k, v)
  		if err != nil {
  			return err
  		}
  		cpy.insert(k, v)
  		return nil
  	})
  	if err != nil {
  		return nil, err
  	}
  	return cpy, nil
  }
docs: // Map returns a new Object constructed by mapping each element in the object
  // using the function f.