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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 canonical(request, uploaded_at, file_id):
 """ Redirect to the current url of a public file """

    filer_file = get_object_or_404(File, pk=file_id, is_public=True)
    if (uploaded_at != filer_file.uploaded_at.strftime('%s') or
            not filer_file.file):
        raise Http404('No %s matches the given query.' %
                      File._meta.object_name)
    return redirect(filer_file.url)