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: helpers.rs
    path of file: ./repos/kani/library/kani_macros/src/sysroot/contracts
    
    the code of the file until where you have to start completion: // Copyright Kani Contributors
// SPDX-License-Identifier: Apache-2.0 OR MIT

//! Functions that operate third party data structures with no logic that is
//! specific to Kani and contracts.

use proc_macro2::{Ident, Span};
use quote::{quote, ToTokens};

    
fn hash_of_token_stream<H: std::hash::Hasher>(hasher: &mut H, stream: proc_macro2::TokenStream) {
    use proc_macro2::TokenTree;
    use std::hash::Hash;
    for token in stream {
        match token {
            TokenTree::Ident(i) => i.hash(hasher),
            TokenTree::Punct(p) => p.as_char().hash(hasher),
            TokenTree::Group(g) => {
                std::mem::discriminant(&g.delimiter()).hash(hasher);
                hash_of_token_stream(hasher, g.stream());
            }
            TokenTree::Literal(lit) => lit.to_string().hash(hasher),
        }
    }
}