By passing both ``app`` and ``checkout``, the ``importmap()`` function will

output the ``importmap`` and also add a ``<script type="module">`` tag that

loads the ``app.js`` file *and* the ``checkout.js`` file. It's important

to *not* call ``parent()`` in the ``importmap`` block. Each page can only

have *one* importmap, so ``importmap()`` must be called exactly once.

If, for some reason, you want to execute *only* ``checkout.js``

and *not* ``app.js``, pass only ``checkout`` to ``importmap()``.

The ``importmap()`` function always includes the full import map to ensure all

module definitions are available on the page. It also adds a ``<script type="module">``

tag to load the specific JavaScript entry files you pass to it (in the example

above, the ``app.js`` file *and* the ``checkout.js`` file).

..warning::

Do not call ``parent()`` inside the ``{% block importmap %}`` Twig block. Each

page can include only one import map, so ``importmap()`` must be called exactly once.

If you want to execute *only* ``checkout.js`` (and not ``app.js``), call

``{{ importmap('checkout') }}``. In this case, the full import map will still be

included in the page, but only the ``checkout.js`` file will actually be loaded.

Using a Content Security Policy (CSP)