code: func (idx *sessionIndex) chunkFileNames() []string {
  	fileNames := make([]string, len(idx.chunks))
  	for i := 0; i < len(idx.chunks); i++ {
  		fileNames[i] = idx.chunksFileName(i)
  	}
  	return fileNames
  }
docs: // chunkFileNames returns file names of all session chunk files