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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 run_export_media(filename=None):
 """ Exports the media folder on the server. Usage:: fab prod run_export_media fab prod run_export_media:filename=foobar.tar.gz """

    if not filename:
        filename = settings.MEDIA_DUMP_FILENAME

    with cd(settings.FAB_SETTING('SERVER_MEDIA_ROOT')):
        run('rm -rf {0}'.format(filename))
        run('tar -czf {0} *'.format(filename))
        run('mv {0} {1}'.format(
            filename, settings.FAB_SETTING('SERVER_MEDIA_BACKUP_DIR')))