code: def advance_for_next_slice(self, recovery_slice=False):
      
      if recovery_slice:
        self.slice_id += 2
        # Restore input reader to the beginning of the slice.
        self.input_reader = self.input_reader.from_json(self._input_reader_json)
      else:
        self.slice_id += 1
docs: Advance relavent states for next slice.
  
      Args:
        recovery_slice: True if this slice is running recovery logic.
          See handlers.MapperWorkerCallbackHandler._attempt_slice_recovery
          for more info.