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: broker.rs
    path of file: ./repos/mqtt_rs/src
    
    the code of the file until where you have to start completion: use std::rc::{Rc};
use std::cell::{RefCell};
use std::collections::HashMap;

//is same identity
fn is_same<T>(lhs: &T, rhs: &T) -> bool {
    lhs as *const T == rhs as *const T
}

//the code below is horrible
//borrow doesn't return T, it returns Ref<T>
//we need to dereference it to get to the T inside
//is_same takes borrow so reapply the ampersand
fn is_same_subscriber<T: Subscriber>(lhs: Rc<RefCell<T>>, rhs: Rc<RefCell<T>>) -> bool {
    let lhs = lhs.clone();
    let rhs = rhs.clone();
    let res = is_same(&*lhs.borrow(), &*rhs.borrow()); //needed to live long enough
    res
}

pub trait Subscriber {
    fn new_message(&mut self, bytes: &[u8]);
}

pub struct Broker<T: Subscriber> {
    tree: Node<T>,
    use_cache: bool,
    cache: HashMap<String, Vec<Rc<RefCell<T>>>>,
}

struct Node<T: Subscriber> {
    children: HashMap<String, Node<T>>,
    leaves: Vec<Subscription<T>>,
}

struct Subscription<T: S
    
    fn publish_impl(tree: &Node<T>, pub_parts: &[&str], payload: &[u8], topic: &str, use_cache: bool, cache: &mut HashMap<String, Vec<Rc<RefCell<T>>>>) {
        if pub_parts.len() < 1 {
            return;
        }

        let part = &pub_parts[0][..];
        let pub_parts = &pub_parts[1..];

        for part in vec![part, "#", "+"] {

            if let Some(node) = tree.children.get(part) {
                if pub_parts.len() == 0 || part == "#" {
                    Self::publish_node(&node, payload, topic, use_cache, cache);
                }

                //so that "finance/#" matches "finance"
                if pub_parts.len() == 0 && node.children.contains_key("#") {
                    Self::publish_node(node.children.get("#")
                                       .expect(&format!("Could not get node at {}", &part)),
                                       payload, topic, use_cache, cache);
                }

                Self::publish_impl(&node, pub_parts, payload, topic, use_cache, cache);
            }
        }
    }