code: func (p *nasDatastoreMountProcessor) validateDatastore(ds *object.Datastore) error {
  	if p.ds == nil {
  		p.ds = ds
  		return nil
  	}
  	expected := p.ds.Reference().Value
  	actual := ds.Reference().Value
  	if expected != actual {
  		return fmt.Errorf("expected datastore ID to be %q, got %q", expected, actual)
  	}
  	return nil
  }
docs: // validateDatastore does one of two things: either stores the current
  // datastore in the processor, if it's missing, or validates the supplied
  // datastore with the one currently in the processor by checking if their IDs
  // match.