feat: + cross_validate, trait Predictor, refactoring

src/base.rs

@@ -0,0 +1,10 @@
+//! # Common Interfaces and methods
+//!
+//! This module consolidates interfaces and uniform basic API that is used elsewhere in the code.
+
+use crate::error::Failed;
+
+/// Implements method predict that offers a way to estimate target value from new data
+pub trait Predictor<X, Y> {
+    fn predict(&self, x: &X) -> Result<Y, Failed>;
+}