code: def _check_compatibility(self):
          
          stored_descr = self._file_trace_description()
          try:
              for k, v in self._model_trace_description():
                  assert(stored_descr[k][0] == v[0])
          except:
              raise ValueError(
                  "The objects to tally are incompatible with the objects stored in the file.")
docs: Make sure the next objects to be tallied are compatible with the
          stored trace.