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: adam.rs
    path of file: ./repos/Rust/src/machine_learning/optimization
    
    the code of the file until where you have to start completion: //! # Adam (Adaptive Moment Estimation) optimizer
//!
//! The `Adam (Adaptive Moment Estimation)` optimizer is an adaptive learning rate algorithm used
//! in gradient descent and machine learning, such as for training neural networks to solve deep
//! learning problems. Boasting memory-efficient fast convergence rates, it sets a
    
    fn test_adam_step_custom_params() {
        let gradients = vec![9.0, -8.0, 7.0, -6.0, 5.0, -4.0, 3.0, -2.0, 1.0];

        let mut optimizer = Adam::new(Some(0.005), Some((0.5, 0.599)), Some(1e-5), 9);
        let updated_params = optimizer.step(&gradients);

        assert_eq!(
            updated_params,
            vec![
                -0.004999994444450618,
                0.004999993750007813,
                -0.004999992857153062,
                0.004999991666680556,
                -0.004999990000020001,
                0.004999987500031251,
                -0.004999983333388888,
                0.004999975000124999,
                -0.0049999500004999945
            ]
        );
    }