code: func (iter *dbCacheIterator) Key() []byte {
  	// Nothing to return if iterator is exhausted.
  	if iter.currentIter == nil {
  		return nil
  	}
  
  	return iter.currentIter.Key()
  }
docs: // Key returns the current key the iterator is pointing to.
  //
  // This is part of the leveldb iterator.Iterator interface implementation.