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: conversion.rs
    path of file: ./repos/burn/crates/burn-tensor/src/tensor/backend
    
    the code of the file until where you have to start completion: use crate::tensor::Shape;
use std::collections::HashMap;

#[derive(Debug)]
pub struct Convertor {
    indices_from: HashMap<usize, Vec<usize>>,
    indices_to: HashMap<Vec<usize>, usize>,
}

impl Convertor {
    pub fn new<const D: usize>(shape: &Shape<D>, order_from: Order, order_to: Order) -> Self {
        Self {
            indices_from: revert_indice
    
    fn should_build_indices_2d_complexe() {
        let shape = Shape::new([2, 3]);

        let indices = build_indices(&shape, Order::Left);

        let expected = HashMap::from([
            (vec![0, 0], 0),
            (vec![0, 1], 1),
            (vec![0, 2], 2),
            (vec![1, 0], 3),
            (vec![1, 1], 4),
            (vec![1, 2], 5),
        ]);

        assert_eq!(expected, indices);
    }