feat: Make SerDe optional

src/metrics/f1.rs

@@ -18,7 +18,7 @@
 //!
 //! <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
 //! <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script>
-use serde::{Deserialize, Serialize};
+#[cfg(feature = "serde")] use serde::{Deserialize, Serialize};
 
 use crate::linalg::BaseVector;
 use crate::math::num::RealNumber;
@@ -26,7 +26,8 @@ use crate::metrics::precision::Precision;
 use crate::metrics::recall::Recall;
 
 /// F-measure
-#[derive(Serialize, Deserialize, Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug)]
 pub struct F1<T: RealNumber> {
     /// a positive real factor
     pub beta: T,