code: def _model_unpickle(cls, data):
      
      auto_field_value = data['pk']
      try:
          obj = cls.objects.get(pk=auto_field_value)
      except Exception as e:
          if isinstance(e, OperationalError):
              # Attempt reconnect, we've probably hit;
              # OperationalError(2006, 'MySQL server has gone away')
              logger.debug("Caught OperationalError, closing database connection.", exc_info=e)
              from django.db import connection
              connection.close()
              obj = cls.objects.get(pk=auto_field_value)
          else:
              raise
      return obj
docs: Unpickle a model by retrieving it from the database.