pub(crate) fn include_module(&self, target_module: Module) -> bool {
        let mut module = *self;
        loop {
            let true_module = module.real_module();
            if true_module.id() == target_module.id() {
                return true;
            };
            match module.upper() {
                Some(upper) => module = upper,
                None => break,
            }
        }
        false
    }
Check whether `target_module` exists in the ancestors of `self`.
ruruby/src/value/class.rs