feat: Make SerDe optional

src/linear/logistic_regression.rs

@@ -56,7 +56,7 @@ use std::cmp::Ordering;
 use std::fmt::Debug;
 use std::marker::PhantomData;
 
-use serde::{Deserialize, Serialize};
+#[cfg(feature = "serde")] use serde::{Deserialize, Serialize};
 
 use crate::api::{Predictor, SupervisedEstimator};
 use crate::error::Failed;
@@ -68,11 +68,13 @@ use crate::optimization::line_search::Backtracking;
 use crate::optimization::FunctionOrder;
 
 /// Logistic Regression parameters
-#[derive(Serialize, Deserialize, Debug, Clone)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone)]
 pub struct LogisticRegressionParameters {}
 
 /// Logistic Regression
-#[derive(Serialize, Deserialize, Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug)]
 pub struct LogisticRegression<T: RealNumber, M: Matrix<T>> {
     coefficients: M,
     intercept: M,