code: function () {                                                        // 68
      var self = this;                                                          // 69
      var clone = new IdMap(self._idStringify, self._idParse);                  // 70
      self.forEach(function (value, id) {                                       // 71
        clone.set(id, EJSON.clone(value));                                      // 72
      });                                                                       // 73
      return clone;                                                             // 74
    }
docs: 65 Assumes that values are EJSON-cloneable, and that we don't need to clone IDs (ie, that nobody is going to mutate an ObjectId).                    // 67