code: func (iter *dbCacheIterator) Last() bool {
  	// Seek to the last key in both the database and cache iterators and
  	// choose the iterator that is both valid and has the larger key.
  	iter.dbIter.Last()
  	iter.cacheIter.Last()
  	return iter.chooseIterator(false)
  }
docs: // Last positions the iterator at the last key/value pair and returns whether or
  // not the pair exists.
  //
  // This is part of the leveldb iterator.Iterator interface implementation.