code: func (pool *ReaderPool) segmentsToString(infos []*SegmentCommitInfo) string {
  	// TODO synchronized
  	var parts []string
  	for _, info := range infos {
  		parts = append(parts, pool.segmentToString(info))
  	}
  	return strings.Join(parts, " ")
  }
docs: /*
  returns a string description of the specified segments, for debugging.
  */