code: func MustBeRunning(d Driver) error {
  	s, err := d.GetState()
  	if err != nil {
  		return err
  	}
  
  	if s != state.Running {
  		return ErrHostIsNotRunning
  	}
  
  	return nil
  }
docs: // MustBeRunning will return an error if the machine is not in a running state.