How to use the green.config.mergeConfig function in green

Returns the number of tests that failed.
            """
            # Django setup
            self.setup_test_environment()
            django_db = self.setup_databases()

            # Green
            if type(test_labels) == tuple:
                test_labels = list(test_labels)
            else:
                raise ValueError("test_labels should be a tuple of strings")
            if not test_labels:
                test_labels = ['.']

            args = mergeConfig(Namespace())
            if self.verbose != -1:
                args.verbose = self.verbose
            args.targets = test_labels
            stream = GreenStream(sys.stdout)
            suite = self.loader.loadTargets(args.targets)
            if not suite:
                suite = GreenTestSuite()
            result = run(suite, stream, args)

            # Django teardown
            self.teardown_databases(django_db)
            self.teardown_test_environment()
            return self.suite_result(suite, result)