code: func (c *PCPClient) SetFlag(flag MMVFlag) error {
  	c.mutex.Lock()
  	defer c.mutex.Unlock()
  
  	if c.r.mapped {
  		return errors.New("cannot set mmv flag for an active client")
  	}
  
  	c.flag = flag
  	return nil
  }
docs: // SetFlag sets the MMVflag for the client