Parse and store snapshot hits.

def _parse_snapshot_hits(self, file_obj):
        """Parse and store snapshot hits."""
        for _ in range(self.n_snapshot_hits):
            dom_id, pmt_id = unpack('<ib', file_obj.read(5))
            tdc_time = unpack('>I', file_obj.read(4))[0]
            tot = unpack('<b', file_obj.read(1))[0]
            self.snapshot_hits.append((dom_id, pmt_id, tdc_time, tot))