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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 download_file(request):
    '''Create and download a zip file containing the media file.'''
    if request.method == "GET":
        if path.exists(settings.MEDIA_ROOT):
            zipfile_name = 'media_%s.zip' % settings.SITE_NAME
            in_memory_file = BytesIO()

            media_zipfile = zipfile.ZipFile(in_memory_file, 'w',
                                            zipfile.ZIP_DEFLATED)

            directory_name = path.split(settings.MEDIA_ROOT)[-1]
            for root, dirs, files in walk(directory_name):
                for file in files:
                    media_zipfile.write(path.join(root, file))

            media_zipfile.close()

            resp = HttpResponse(in_memory_file.getvalue(),
                                content_type="application/x-zip-compressed")
            resp['Content-Disposition'] = (
                'attachment; filename=%s' % zipfile_name)

        else:
            resp = render(request,
                          'django_admin/transfer_media_message.html',
                          {'error_message':
                           'media file does not exist'})
    else:
        resp = HttpResponseNotAllowed(permitted_methods=['GET'])

    return resp