code: func (s *IndicesFlushService) Force(force bool) *IndicesFlushService {
  	s.force = &force
  	return s
  }
docs: // Force indicates whether a flush should be forced even if it is not
  // necessarily needed ie. if no changes will be committed to the index.
  // This is useful if transaction log IDs should be incremented even if
  // no uncommitted changes are present. (This setting can be considered as internal).