def METHOD_NAME(self):
    # The body only passes the skimpiest of requirements by having 'index'
    # as the only root-level key, and having a 'dict' as its value
    if len(self.body) == 1:
        if 'index' in self.body:
            if isinstance(self.body['index'], dict):
                return True
    raise ConfigurationError(f'Bad value for "index_settings": {self.body}')