Serialization order problem

gistfile1.js

'use strict';

var transit = require('transit-js');
var I = require('immutable');

var wCache = I.Map();
var wid = 0;

var listHandler = transit.makeWriteHandler({
  tag: function(v) {
    if (wCache.get(v) != null) {
      return 'cacheL';
    }
    return 'List';
  },
  rep: function(v) {
    var id = wCache.get(v);
    if (id != null) {
      return id;
    }
    wCache = wCache.set(v, wid++);
    // shallow. Let transit convert each cell recursively
    return v.toArray();
  },
  stringRep: function() {return null;},
});

var writer = transit.writer('json', {
  handlers: transit.map([
    I.List, listHandler,
  ])
});

var rCache = I.Map();
var rid = 0;

var reader = transit.reader('json', {
  handlers: {
    List: function(v) {
      console.log('----------', rid, v);
      var ret = I.List(v);
      rCache = rCache.set(rid++, ret);
      return ret;
    },
    cacheL: function(v) {
      console.log('cache', v);
      return rCache.get(v);
    },
  }
});

var obj = I.List([
  I.List([1]),
  I.List([1]),
]);

var res = writer.write(obj);
var res2 = reader.read(res);
console.log('r', res);
console.log();
console.log('o', obj);
console.log('w', res2);
// console.log(obj.get(1));
// console.log(res2.get(1));
// console.log(obj.equals(res2));
console.log();
console.log(wCache);
console.log(rCache);