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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_unique(self):
 """ Add this method because django doesn't validate correctly because required fields are excluded. """

        unique_checks, date_checks = self.instance._get_unique_checks(exclude=[])
        errors = self.instance._perform_unique_checks(unique_checks)
        if errors:
            self.add_error(None, errors)