code: func (mc MongoClient) UpdateInterval(interval contract.Interval) error {
  	var mapped models.Interval
  	id, err := mapped.FromContract(interval)
  	if err != nil {
  		return err
  	}
  
  	mapped.TimestampForUpdate()
  
  	return mc.updateId(db.Interval, id, mapped)
  }
docs: // Update an Interval
  // UnexpectedError - failed to update interval in the database