feat: Make SerDe optional

src/error/mod.rs

@@ -2,10 +2,11 @@
 use std::error::Error;
 use std::fmt;
 
-use serde::{Deserialize, Serialize};
+#[cfg(feature = "serde")] use serde::{Deserialize, Serialize};
 
 /// Generic error to be raised when something goes wrong.
-#[derive(Debug, Serialize, Deserialize)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug)]
 pub struct Failed {
     err: FailedError,
     msg: String,
@@ -13,7 +14,8 @@ pub struct Failed {
 
 /// Type of error
 #[non_exhaustive]
-#[derive(Copy, Clone, Debug, Serialize, Deserialize)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Copy, Clone, Debug)]
 pub enum FailedError {
     /// Can't fit algorithm to data
     FitFailed = 1,