code: def get_alerts_since(self, timestamp):
          
          unix_timestamp = timeformatutils.to_UNIXtime(timestamp)
          result = []
          for alert in self.alerts:
              if alert.last_update >= unix_timestamp:
                  result.append(alert)
          return result
docs: Returns all the `Alert` objects of this `Trigger` that were fired since the specified timestamp.
          :param timestamp: time object representing the point in time since when alerts have to be fetched
          :type timestamp: int, ``datetime.datetime`` or ISO8601-formatted string
          :return: list of `Alert` instances