code: func (it *Iterator) Next() bool {
  	for it.nodeIt.Next(true) {
  		if it.nodeIt.Leaf() {
  			it.Key = it.nodeIt.LeafKey()
  			it.Value = it.nodeIt.LeafBlob()
  			return true
  		}
  	}
  	it.Key = nil
  	it.Value = nil
  	it.Err = it.nodeIt.Error()
  	return false
  }
docs: // Next moves the iterator forward one key-value entry.