code: func (s *ReindexService) WaitForActiveShards(waitForActiveShards string) *ReindexService {
  	s.waitForActiveShards = waitForActiveShards
  	return s
  }
docs: // WaitForActiveShards sets the number of shard copies that must be active before
  // proceeding with the reindex operation. Defaults to 1, meaning the primary shard only.
  // Set to `all` for all shard copies, otherwise set to any non-negative value less than or
  // equal to the total number of copies for the shard (number of replicas + 1).