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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _validate_backend(self):
 """ ensure backend string representation is correct """

        try:
            self.backend_class
        # if we get an import error the specified path is wrong
        except (ImportError, AttributeError) as e:
            raise ValidationError(_('No valid backend found, got the following python exception: "%s"') % e)