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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 get_metar_from_mission( mission_file: str, icao: str = 'XXXX', time: str = None, ) -> str: """ Builds a dummy METAR string from a mission file Args: mission_file: input mission file icao: dummy ICAO (defaults to XXXX) time: dummy time (defaults to now()) Returns: METAR str """

    return _MetarFromMission(
        mission_file=mission_file,
        icao=icao,
        time=time,
    ).metar