code: function (rawData, model) {
      if (_.isNull(rawData) || _.isUndefined(rawData)) return '';
      return this._convert(rawData);
    }
docs: Converts an ISO-8601 formatted datetime string to a datetime string, date
  string or a time string. The timezone is ignored if supplied.
  
  @member Backgrid.DatetimeFormatter
  @param {string} rawData
  @param {Backbone.Model} model Used for more complicated formatting
  @return {string|null|undefined} ISO-8601 string in UTC. Null and undefined
  values are returned as is.