code: func (s *BulkService) WaitForActiveShards(waitForActiveShards string) *BulkService {
  	s.waitForActiveShards = waitForActiveShards
  	return s
  }
docs: // WaitForActiveShards sets the number of shard copies that must be active
  // before proceeding with the bulk 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).