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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 parse(station: str, txt: str) -> (MetarData, Units):
 # type: ignore """ Returns MetarData and Units dataclasses with parsed data and their associated units """

    core.valid_station(station)
    return parse_na(txt) if core.uses_na_format(station[:2]) else parse_in(txt)