How to use the @uifabric/example-data.isGroupable function in @uifabric/example-data

name: 'A to Z',
        iconProps: { iconName: 'SortUp' },
        canCheck: true,
        checked: column.isSorted && !column.isSortedDescending,
        onClick: () => this._onSortColumn(column.key, false)
      },
      {
        key: 'zToA',
        name: 'Z to A',
        iconProps: { iconName: 'SortDown' },
        canCheck: true,
        checked: column.isSorted && column.isSortedDescending,
        onClick: () => this._onSortColumn(column.key, true)
      }
    ];
    if (isGroupable(column.key)) {
      items.push({
        key: 'groupBy',
        name: 'Group by ' + column.name,
        iconProps: { iconName: 'GroupedDescending' },
        canCheck: true,
        checked: column.isGrouped,
        onClick: () => this._onGroupByColumn(column)
      });
    }
    return {
      items: items,
      target: ev.currentTarget as HTMLElement,
      directionalHint: DirectionalHint.bottomLeftEdge,
      gapSpace: 10,
      isBeakVisible: true,
      onDismiss: this._onContextualMenuDismissed