er</td>
      <td>String or Function</td>
      <td>'order'</td>
      <td>Order the groups by a field name or custom sort function.
        By default, groups are ordered by a property <code>order</code> (if set).
        If no <code>order</code> properties are provided, the order will be undetermined.
      </td>
    </tr>

    <tr>
      <td>groupOrderSwap</td>
      <td>Function</td>
      <td>none</td>
      <td>Swaps the positions of two groups. If groups have a custom order (via <code>groupOrder</cod