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: k_nearest_neighbors.rs
    path of file: ./repos/RustQuant/src/ml
    
    the code of the file until where you have to start completion: /*
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
RustQuant: A Rust library for quantitative finance tools.
Copyright (C) 2023 https://github.com/avhz
Dual licensed under Apache 2.0 and MIT.
See:
     - LICENSE-APACHE.md
     - LICENSE-MIT.md
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/

//! Module for K nearest neighbors (KNN) algorithms.

// ~~~~~~~~~
    
    fn predict_one(&self, xprime: &DMatrix<f64>, k: usize) -> f64 {
        let neighbors = self.find_neighbors(xprime, k);

        let mut classes: Vec<f64> = vec![0.0; neighbors.len()];
        for i in 0..neighbors.len() {
            classes[i] = self.y[neighbors[i].0];
        }

        let mut counts = HashMap::new();

        classes
            .iter()
            .copied()
            .max_by_key(|&val| {
                let count = counts.entry(val as i64).or_insert(0);
                *count += 1;
                *count
            })
            .unwrap()
    }