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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 _calculate_bounds(self):
 """Calculate beginning and end of log events."""

        # get start datetime
        first = self.coll_handle.find_one(None, sort=[("ts", ASCENDING)])
        last = self.coll_handle.find_one(None, sort=[("ts", DESCENDING)])

        self._start = first['ts']
        if self._start.tzinfo is None:
            self._start = self._start.replace(tzinfo=tzutc())

        self._end = last['ts']
        if self._end.tzinfo is None:
            self._end = self._end.replace(tzinfo=tzutc())

        return True