Function brute_force_knn 

pub fn brute_force_knn(
    x: &[f32],
    y: &[f32],
    z: &[f32],
    qx: f32,
    qy: f32,
    qz: f32,
    k: usize,
) -> Vec<Neighbor>

Finds up to k nearest neighbors by brute force.