fn prepend(vm: &mut VM, self_val: Value, _args: &Args2) -> VMResult {
    let self_mod = self_val.into_module();
    for arg in vm.args().to_owned() {
        let module = arg.expect_module("arg")?;
        self_val
            .into_module()
            .append_prepend(&mut vm.globals, self_mod, module);
    }
    Ok(self_val)
}
Module#prepend(*modules) -> self
https://docs.ruby-lang.org/ja/latest/method/Module/i/prepend.html
ruruby/src/builtin/module.rs