code: func (iter *MockStateRangeQueryIterator) Close() error {
  	if iter.Closed == true {
  		err := errors.New("MockStateRangeQueryIterator.Close() called after Close()")
  		mockLogger.Errorf("%+v", err)
  		return err
  	}
  
  	iter.Closed = true
  	return nil
  }
docs: // Close closes the range query iterator. This should be called when done
  // reading from the iterator to free up resources.