Can only open, not close a panel

[jstray]

Clicking on the panel header opens it, but clicking on it again it flashes closed for a moment and then re-opens. I would expect it to toggle

        <Collapse>
          <Panel header='Output'>
            <DataGrid idProperty="index" dataSource={tableData} columns={columns} />
          </Panel>
        </Collapse>

There is only one panel in this example, but it happens even if I add another panel. This is under Bootstrap 4.

[jstray]

Solved: need to include CSS

require('rc-collapse/assets/index.css');

[shepherdwind]

Document file updated now.