pub fn simple_linear_regression_prediction<T>( train: &Vec<(T, T)>, test: &Vec<(T, T)>, ) -> Vec<T>where T: Sum<T> + Div<Output = T> + Debug + Display + Add + Copy + Add<T, Output = T> + Sub<T, Output = T> + Mul<T, Output = T> + FromStr, <T as FromStr>::Err: Debug,