code: func (c *RadioGroup) SetSelected(id int) bool {
  	found := false
  	if id < 0 || id >= len(c.items) {
  		return false
  	}
  
  	for idx, item := range c.items {
  		if idx == id {
  			found = true
  			item.SetSelected(true)
  		} else {
  			item.SetSelected(false)
  		}
  	}
  
  	return found
  }
docs: // SetSelected selects the radio by its number. The function
  // returns false if the number is invalid for the radio group