fn key_value_pair_with_target_size(seed: i32, target_size_byte: usize) -> (Vec<u8>, Vec<u8>) {
    let mut key = vec![0; target_size_byte - 4];
    key.put_i32(seed);

    let mut val = vec![0; target_size_byte - 4];
    val.put_i32(seed);

    (key, val)
}
Create a key value pair where key and value are of target size in bytes
mini-lsm/src/tests/week2_day5.rs