code: func (m *Manager) HistoricalInterval(ctx context.Context) (IntervalList, error) {
  	var pm mo.PerformanceManager
  
  	err := m.Properties(ctx, m.Reference(), []string{"historicalInterval"}, &pm)
  	if err != nil {
  		return nil, err
  	}
  
  	return IntervalList(pm.HistoricalInterval), nil
  }
docs: // HistoricalInterval gets the PerformanceManager.HistoricalInterval property and wraps as an IntervalList.