def _store_timestamp(self, timestamp):
        if getattr(self, 'first_timestamp', None) is None:
            self.first_timestamp = timestamp
            LOG.debug("Storing %d as the first timestamp of the trace file %s",
                    self.first_timestamp, self.filename)
If not already saved, cache the first timestamp in the active trace
dataset/ETHPy150Open openxc/openxc-python/openxc/sources/trace.py/TraceDataSource._store_timestamp