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: fixme_append.rs
    path of file: ./repos/kani/tests/kani/Vectors/any
    
    the code of the file until where you have to start completion: // Copyright Kani Contributors
// SPDX-License-Identifier: Apache-2.0 OR MIT

/// Append 2 arbitrary vectors, lengths at most 1 and 2 respectively,
/// and assert they have been appended.  This test case takes 53
/// minutes with #[kani::unwind(75)], but takes 
    
fn main() {
    let mut v1: Vec<u128> = kani::vec::any_vec::<_, 1>();
    kani::assume(v1.len() == 1);
    let mut v2: Vec<u128> = kani::vec::any_vec::<_, 2>();
    kani::assume(v2.len() == 2);

    let v1_initial = v1.clone();
    let v2_initial = v2.clone();
    let l1 = v1.len();
    let l2 = v2.len();

    v1.append(&mut v2);
    assert!(v2.len() == 0);
    assert!(v1.len() == (l1 + l2));

    assert!(v1[0..l1] == v1_initial);
    assert!(v1[l1..] == v2_initial);
}