code: function() {
          var datePickerMap = {};
          var columnModelMap = this.columnModel.get('columnModelMap');
  
          _.each(columnModelMap, function(columnModel) {
              var name = columnModel.name;
              var component = columnModel.component;
              var options;
  
              if (component && component.name === 'datePicker') {
                  options = component.options || {};
  
                  datePickerMap[name] = new DatePicker(this.$el, options);
  
                  this._bindEventOnDatePicker(datePickerMap[name]);
              }
          }, this);
  
          return datePickerMap;
      }
docs: Creates instances map of 'tui-date-picker'
  @returns {Object.<string, DatePicker>}
  @private