feat: Make SerDe optional

src/cluster/kmeans.rs

@@ -56,7 +56,7 @@ use rand::Rng;
 use std::fmt::Debug;
 use std::iter::Sum;
 
-use serde::{Deserialize, Serialize};
+#[cfg(feature = "serde")] use serde::{Deserialize, Serialize};
 
 use crate::algorithm::neighbour::bbd_tree::BBDTree;
 use crate::api::{Predictor, UnsupervisedEstimator};
@@ -66,7 +66,8 @@ use crate::math::distance::euclidian::*;
 use crate::math::num::RealNumber;
 
 /// K-Means clustering algorithm
-#[derive(Serialize, Deserialize, Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug)]
 pub struct KMeans<T: RealNumber> {
     k: usize,
     y: Vec<usize>,