code: func (l AncestorList) GetParentOf(workItemID uuid.UUID) *Ancestor {
  	for _, a := range l {
  		if a.DirectChildID == workItemID {
  			return &a
  		}
  	}
  	return nil
  }
docs: // GetParentOf returns the first parent item that we can find in the list of
  // ancestors; otherwise nil is returned.