code: func (it *iterator) Next() bool {
  	// If the iterator was not yet initialized, do it now
  	if !it.inited {
  		it.inited = true
  		return len(it.keys) > 0
  	}
  	// Iterator already initialize, advance it
  	if len(it.keys) > 0 {
  		it.keys = it.keys[1:]
  		it.values = it.values[1:]
  	}
  	return len(it.keys) > 0
  }
docs: // Next moves the iterator to the next key/value pair. It returns whether the
  // iterator is exhausted.