code: func _show(i interface{}) string {
  	if i == nil {
  		return ""
  	}
  	if v, ok := i.([]byte); ok {
  		return string(v)
  	}
  	if v, ok := i.(string); ok {
  		return v
  	}
  	if v, ok := i.(*Graph); ok {
  		return v.Show()
  	}
  	return fmt.Sprint(i)
  }
docs: // _show: this function is used in tests