Persistent memory usage despite object deletion in Rust

use std::rc::Rc; use std::cell::RefCell; 

#[derive(Debug)]
struct Node {
    value: i32,
    children: RefCell<Vec<Rc<Node>>>,
}

impl Node {
    fn new(value: i32) -> Rc<Node> {
        Rc::new(Node {
            value,
            children: RefCell::new(Vec::new()),
        })
    }
    fn add_child(&self, child: Rc<Node>) {
        self.children.borrow_mut().push(child);
    }
}

fn create_graph() -> Rc<Node> {
    let node1 = Node::new(1);
    let node2 = Node::new(2);
    node1.add_child(node2.clone());
    node2.add_child(node1.clone());
    node1
}

fn main() {
    let _graph = create_graph();
    // Memory should be deallocated here, but it isn't.
}