splayed as a range.
        If not, the item is displayed as a box.</td>
    </tr>
    <tr>
      <td>group</td>
      <td>any type</td>
      <td>no</td>
      <td>This field is optional. When the group column is provided,
        all items with the same group are placed on one line.
        A vertical axis is displayed showing the groups.
        Grouping items can be useful for example when showing availability of multiple
        people, rooms, or other resources next to each other.<br>
      </td>
    