code: def first_timestamp(self, sid, epoch=False):
          
          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
docs: 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