code: func (it *Not) Close() error {
  	err := it.primaryIt.Close()
  
  	_err := it.allIt.Close()
  	if _err != nil && err == nil {
  		err = _err
  	}
  
  	return err
  }
docs: // Close closes the primary and all iterators.  It closes all subiterators
  // it can, but returns the first error it encounters.