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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 cast_naive_datetime_to_tz(dt, tz=UTC()):
 """If datetime is tz-naive, set it to ``tz``. If datetime is tz-aware, return it unmodified. Args: dt : datetime tz-naive or tz-aware datetime. tz : datetime.tzinfo The timezone to which to adjust tz-naive datetime. Returns: datetime tz-aware datetime. Warning: This will change the actual moment in time that is represented if the datetime is naive and represents a date and time not in ``tz``. See Also: ``normalize_datetime_to_utc()`` """

    if has_tz(dt):
        return dt
    return dt.replace(tzinfo=tz)