code: def validate_instance(self, instance, import_validation_errors=None, validate_unique=True):
          
          if import_validation_errors is None:
              errors = {}
          else:
              errors = import_validation_errors.copy()
          if self._meta.clean_model_instances:
              try:
                  instance.full_clean(
                      exclude=errors.keys(),
                      validate_unique=validate_unique,
                  )
              except ValidationError as e:
                  errors = e.update_error_dict(errors)
  
          if errors:
              raise ValidationError(errors)
docs: Takes any validation errors that were raised by
          :meth:`~import_export.resources.Resource.import_obj`, and combines them
          with validation errors raised by the instance's ``full_clean()``
          method. The combined errors are then re-raised as single, multi-field
          ValidationError.
  
          If the ``clean_model_instances`` option is False, the instances's
          ``full_clean()`` method is not called, and only the errors raised by
          ``import_obj()`` are re-raised.