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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 _add_tzinfo(self, datetime_obj, tz_string):
 """ take a naive datetime and add dateutil.tz.tzinfo object :param datetime_obj: naive datetime object :return: datetime object with tzinfo """

        if datetime_obj is None:
            return None

        tzinfo_match = tz.gettz(tz_string)
        return datetime_obj.replace(tzinfo=tzinfo_match)