code: func (d *ResourceDiff) SetNewComputed(key string) error {
  	if err := d.checkKey(key, "SetNewComputed", false); err != nil {
  		return err
  	}
  
  	return d.setDiff(key, nil, true)
  }
docs: // SetNewComputed functions like SetNew, except that it blanks out a new value
  // and marks it as computed.
  //
  // This function is only allowed on computed attributes.