code: func (bf *BFlags) AddBool(name string, def bool) *Flag {
  	flag := bf.addFlag(name, boolType)
  	if flag == nil {
  		return nil
  	}
  	if def {
  		flag.Value = "true"
  	} else {
  		flag.Value = "false"
  	}
  	return flag
  }
docs: // AddBool adds a bool flag to BFlags
  // Note, any error will be generated when Parse() is called (see Parse).