code: func (iter *dbCacheIterator) Prev() bool {
  	// Nothing to return if cursor is exhausted.
  	if iter.currentIter == nil {
  		return false
  	}
  
  	// Move the current iterator to the previous entry and choose the
  	// iterator that is both valid and has the larger key.
  	iter.currentIter.Prev()
  	return iter.chooseIterator(false)
  }
docs: // Prev moves the iterator one key/value pair backward and returns whether or
  // not the pair exists.
  //
  // This is part of the leveldb iterator.Iterator interface implementation.