fn each(vm: &mut VM, self_val: Value, args: &Args2) -> VMResult {
    args.check_args_num(0)?;
    let hash = self_val.as_hash().unwrap();
    let block = args.expect_block()?;
    for (k, v) in hash.iter() {
        vm.eval_block2(&block, k, v)?;
    }

    Ok(self_val)
}
Hash#each, Hash#each_pair
https://docs.ruby-lang.org/ja/latest/method/Hash/i/each.html
ruruby/src/builtin/hash.rs