docs: def _mark_received(self, tsn):
          """
          Mark an incoming data TSN as received.
          """
          # it's a duplicate
          if uint32_gte(self._last_received_tsn, tsn) or tsn in self._sack_misordered:
              self._sack_duplicates.append(tsn)
              return True
  
          # consolidate misordered entries
          self._sack_misordered.add(tsn)
          for tsn in sorted(self._sack_misordered):
              if tsn == tsn_plus_one(self._last_received_tsn):
                  self._last_received_tsn = tsn
              else:
                  break
  
          # filter out obsolete entries
          def is_obsolete(x):
              return uint32_gt(x, self._last_received_tsn)
          self._sack_duplicates = list(filter(is_obsolete, self._sack_duplicates))
          self._sack_misordered = set(filter(is_obsolete, self._sack_misordered))