code: func Open(dbFile string, opts *kv.Options) (*kv.DB, error) {
  	createOpen := kv.Open
  	verb := "opening"
  	if _, err := os.Stat(dbFile); os.IsNotExist(err) {
  		createOpen = kv.Create
  		verb = "creating"
  	}
  	if opts == nil {
  		opts = &kv.Options{}
  	}
  	if opts.Locker == nil {
  		opts.Locker = func(dbFile string) (io.Closer, error) {
  			lkfile := dbFile + ".lock"
  			cl, err := lock.Lock(lkfile)
  			if err != nil {
  				return nil, fmt.Errorf("failed to acquire lock on %s: %v", lkfile, err)
  			}
  			return cl, nil
  		}
  	}
  	if v, _ := strconv.ParseBool(os.Getenv("CAMLI_KV_VERIFY")); v {
  		opts.VerifyDbBeforeOpen = true
  		opts.VerifyDbAfterOpen = true
  		opts.VerifyDbBeforeClose = true
  		opts.VerifyDbAfterClose = true
  	}
  	db, err := createOpen(dbFile, opts)
  	if err != nil {
  		return nil, fmt.Errorf("error %s %s: %v", verb, dbFile, err)
  	}
  	return db, nil
  }
docs: // Open opens the named kv DB file for reading/writing. It
  // creates the file if it does not exist yet.