code: function() {
        var result = Object.create(null);
  
        result.initialized = this.initialized;
        result.rule = this.rule.toJSON();
        result.dtstart = this.dtstart.toJSON();
        result.by_data = this.by_data;
        result.days = this.days;
        result.last = this.last.toJSON();
        result.by_indices = this.by_indices;
        result.occurrence_number = this.occurrence_number;
  
        return result;
      }
docs: Convert iterator into a serialize-able object.  Will preserve current
  iteration sequence to ensure the seamless continuation of the recurrence
  rule.
  @return {Object}