You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: beale.rs
    path of file: ./repos/argmin/crates/argmin-testfunctions/src
    
    the code of the file until where you have to start completion: // Copyright 2018-2024 argmin developers
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

//! # Beale test function
//!
//! Defined as
//!
//! `f(x_1, x_2) = (1.5 - x_1 + x_1 * x
    
        fn test_beale_hessian_finitediff(a in -4.5..4.5, b in -4.5..4.5) {
            let param = [a, b];
            let hessian = beale_hessian(&param);
            let hessian_fd =
                Vec::from(param).forward_hessian(&|x| beale_derivative(&[x[0], x[1]]).to_vec());
            let n = hessian.len();
            for i in 0..n {
                assert_eq!(hessian[i].len(), n);
                for j in 0..n {
                    assert_relative_eq!(
                        hessian[i][j],
                        hessian_fd[i][j],
                        epsilon = 1e-5,
                        max_relative = 1e-2
                    );
                }
            }
        }