如何用rust写一个把对象数组转成树结构的通用方法

serde = { version = "1.0", features = ["derive"] }Copy

use std::collections::HashMap;
use std::fmt::Debug;
use std::hash::Hash;

#[derive(Debug, Clone, Default)]
struct TreeNode<T>
    where T: Clone + Default + Debug
{
    item: T,
    children: Option<Vec<TreeNode<T>>>,
}

impl<T> TreeNode<T>
    where T: Clone + Default + Debug
{
    fn init_tree(items: Vec<T>) -> Vec<TreeNode<T>> {
        let mut tree_items: Vec<TreeNode<T>> = Vec::new();
        for mut item in items {
            let tree = TreeNode { item, ..Default::default() };
            tree_items.push(tree);
        }
        tree_items
    }

    fn set_tree<F1, F2>(tree_items: Vec<TreeNode<T>>, parent_key: String, get_key: F1, get_parent_key: F2) -> Vec<TreeNode<T>>
        where F1: Fn(&T) -> String + Clone,
              F2: Fn(&T) -> String + Clone
    {
        let mut trees: Vec<TreeNode<T>> = Vec::new();
        for mut tree in tree_items.clone() {
            if get_parent_key(&tree.item) == parent_key {
                tree.children = Some(Self::set_tree(tree_items.clone(), get_key(&tree.item), get_key.clone(), get_parent_key.clone()));
                trees.push(tree.clone())
            }
        }
        trees
    }

    fn build_tree<F1,F2>(items: Vec<T>, parent_key: String, get_key: F1, get_parent_key: F2) -> Vec<TreeNode<T>>
        where F1: Fn(&T) -> String + Clone,
              F2: Fn(&T) -> String + Clone
    {
        let items = Self::init_tree(items);
        Self::set_tree(items,parent_key,get_key,get_parent_key)
    }
}


fn main() {
    #[derive(Debug, Clone, Default)]
    struct Item {
        id: String,
        parent_id: Option<String>,
        name: String,
    }

    let items = vec![
        Item {
            id: String::from("1"),
            parent_id: Some(String::from("0")),
            name: String::from("Root"),
        },
        Item {
            id: String::from("2"),
            parent_id: Some(String::from("1")),
            name: String::from("Child 1"),
        },
        Item {
            id: String::from("3"),
            parent_id: Some(String::from("1")),
            name: String::from("Child 2"),
        },
        Item {
            id: String::from("4"),
            parent_id: Some(String::from("2")),
            name: String::from("Grandchild 1.1"),
        },
        Item {
            id: String::from("5"),
            parent_id: Some(String::from("2")),
            name: String::from("Grandchild 1.2"),
        },
    ];

    let tree = TreeNode::build_tree(items,String::from("0"),|i|i.id.clone(),|i|i.parent_id.clone().unwrap().clone());
    println!("tree is {:?}",tree);
}
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