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: nested_borrows.rs
    path of file: ./repos/charon/tests/src
    
    the code of the file until where you have to start completion: //! This module contains functions with nested borrows in their signatures.

pub fn id_mut_mut<'a, 'b, T>(x: &'a mut &'b 
    
pub fn id_mut_pair_test1() {
    let mut x: u32 = 0;
    let px = &mut x;
    let mut p = (px, 1);
    let pp0 = &mut p;
    let pp1 = id_mut_pair(pp0);
    let mut y = 2;
    *pp1 = (&mut y, 3);
}