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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 to_dt(date, default_tz=None):
 """ Returns a non-naive datetime.datetime. Interprets numbers as ms-since-epoch. Parameters date : `int` or `datetime.datetime` The datetime to convert default_tz : tzinfo The TimeZone to use if none is found. If not supplied, and the datetime doesn't have a timezone, then we raise ValueError Returns ------- Non-naive datetime """

    if isinstance(date, (int, long)):
        return ms_to_datetime(date, default_tz)
    elif date.tzinfo is None:
        if default_tz is None:
            raise ValueError("Must specify a TimeZone on incoming data")
        return date.replace(tzinfo=default_tz)
    return date