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: bit_twiddles.rs
    path of file: ./repos/Pleco/pleco/src/core
    
    the code of the file until where you have to start completion: //! Collection of useful functions oriented around modifying singular bits of integer types.
//! You will rarely need to interact with this module directly unless you need functions
//! 
    
pub fn string_u64(input: u64) -> String {
    let mut s = String::new();
    let format_in = format_u64(input);
    for x in 0..8 {
        let slice = &format_in[x * 8..((x * 8) + 8)];
        s += slice;
        s += "\n";
    }
    s
}