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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def export(request, page_id, export_unpublished=False):
 """ API endpoint of this source site to export a part of the page tree rooted at page_id Requests are made by a destination site's import_from_api view. """

    try:
        if export_unpublished:
            root_page = Page.objects.get(id=page_id)
        else:
            root_page = Page.objects.get(id=page_id, live=True)
    except Page.DoesNotExist:
        return JsonResponse({'error': _('page not found')})

    payload = export_pages(root_page, export_unpublished=export_unpublished)

    return JsonResponse(payload)