code: func (it *NodeIterator) Next() bool {
  	// If the iterator failed previously, don't do anything
  	if it.Error != nil {
  		return false
  	}
  	// Otherwise step forward with the iterator and report any errors
  	if err := it.step(); err != nil {
  		it.Error = err
  		return false
  	}
  	return it.retrieve()
  }
docs: // Next moves the iterator to the next node, returning whether there are any
  // further nodes. In case of an internal error this method returns false and
  // sets the Error field to the encountered failure.