code: def _cacheSequenceInfoType(self):
      
  
      hasReset = self.resetFieldName is not None
      hasSequenceId = self.sequenceIdFieldName is not None
  
      if hasReset and not hasSequenceId:
        self._sequenceInfoType = self.SEQUENCEINFO_RESET_ONLY
        self._prevSequenceId = 0
      elif not hasReset and hasSequenceId:
        self._sequenceInfoType = self.SEQUENCEINFO_SEQUENCEID_ONLY
        self._prevSequenceId = None
      elif hasReset and hasSequenceId:
        self._sequenceInfoType = self.SEQUENCEINFO_BOTH
      else:
        self._sequenceInfoType = self.SEQUENCEINFO_NONE
docs: Figure out whether reset, sequenceId,
      both or neither are present in the data.
      Compute once instead of every time.
  
      Taken from filesource.py