// use std::{fmt::Display, io::Write};
// // pub fn writeln<W: Write, D: Display>(writer: &mut W, item: D) -> Result<(), std::io::Error> {
// // write!(writer, "{}\n", item)
// // }
// #[cfg(test)]
// mod test {
// #[test]
// fn writeln_writes_line() {
// let mut buffer: Vec<u8> = Vec::new();
// super::writeln(&mut buffer, "abc").expect("Error writing");
// assert_eq!(b"abc\n", buffer.as_slice());
// }
// }