Rust code explainers

/// A custom iterator that yields Fibonacci numbers up to a maximum value.
pub struct Fibonacci {
    current: u64,
    next: u64,

use std::thread;
 
pub fn parallel_map_reduce<T, M, R, F, G, H>(
    data: &[T],

use std::sync::mpsc;
use std::thread;
use std::time::Duration;