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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 convert_timezone(obj, timezone):
 """Convert `obj` to the timezone `timezone`. Parameters obj : datetime.date or datetime.datetime Returns ------- type(obj) """

    if timezone is None:
        return obj.replace(tzinfo=None)
    return pytz.timezone(timezone).localize(obj)