Function predict 

pub fn predict(x: &f64, model: &[f64; 2]) -> f64

Gives predicted value using model for a given x

use crate::libcaliph::fit::predict;
use float_cmp::approx_eq;

let model = [2.0, 3.5];
let x = 1.5;
let result = predict(&x, &model);
let comparison = 6.5;
assert!(approx_eq!(f64, result, comparison));