Function mean_squared_error 

pub fn mean_squared_error(
    y_true: PyReadonlyArray1<'_, f64>,
    y_pred: PyReadonlyArray1<'_, f64>,
    sample_weight: Option<PyReadonlyArray1<'_, f64>>,
    multioutput: &str,
    squared: bool,
) -> PyResult<f64>

Calculate mean squared error