use std::io::BufRead;
pub fn find_matches(
reader: &mut impl BufRead,
pattern: &str,
writer: &mut impl std::io::Write,
) -> std::io::Result<()> {
for (_i, line) in reader.lines().flat_map(|x| x.ok()).enumerate() {
if line.contains(pattern) {
writeln!(writer, "{}", line)?;
}
}
Ok(())
}