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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 first_timestamp(self, sid, epoch=False):
 """ Get the first available timestamp for a sensor Parameters sid : str SensorID epoch : bool default False If True return as epoch If False return as pd.Timestamp Returns ------- pd.Timestamp | int """

        first_block = self.dbcur.execute(SQL_TMPO_FIRST, (sid,)).fetchone()
        if first_block is None:
            return None

        timestamp = first_block[2]
        if not epoch:
            timestamp = pd.Timestamp.utcfromtimestamp(timestamp)
            timestamp = timestamp.tz_localize('UTC')
        return timestamp