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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 _class_exists(self, classname, namespace):
 """ Test if class defined by classname parameter exists in repository defined by namespace parameter. Returns `True` if class exists and `False` if it does not exist. Exception if the namespace does not exist """

        class_repo = self._get_class_repo(namespace)
        return classname in class_repo