code: func (d *ResourceDiff) NewValueKnown(key string) bool {
  	r := d.get(strings.Split(key, "."), "newDiff")
  	return !r.Computed
  }
docs: // NewValueKnown returns true if the new value for the given key is available
  // as its final value at diff time. If the return value is false, this means
  // either the value is based of interpolation that was unavailable at diff
  // time, or that the value was explicitly marked as computed by SetNewComputed.