fn ser(obj: impl CanonicalSerialize, compress: Compress) -> Vec<u8> {
    let mut serialized = vec![0; obj.serialized_size(compress)];
    obj.serialize_with_mode(&mut serialized[..], compress)?;
    serialized
}

fn deser(bytes: &[u8], validate: Validate) -> Result<MyStruct> {
    let compress = is_it_compressed_or_not(bytes); // this is the part i couldn't find

    let my_struct = Block::deserialize_with_mode(&bytes[..], compress, validate)?
    Ok(my_struct)
}