def __init__(self):
        """Creates an instance of the standalone RMSE metric.

        By default this metric in its initial state will return an RMSE
        value of 0. The metric can be updated by using the `update` method
        while the running RMSE can be retrieved using the `result` method.
        """
        self._mean_RMSE = Mean()
        """The mean utility that will be used to store the running RMSE."""
Creates an instance of the standalone RMSE metric.

        By default this metric in its initial state will return an RMSE
        value of 0. The metric can be updated by using the `update` method
        while the running RMSE can be retrieved using the `result` method.
        
avalanche/evaluation/metrics/rmse.py