fn main() {
    let keyword = vec!["nail", "shoe"];

    build_proverb(&keyword);
}

pub fn build_proverb(list: &[&str]) -> String {
  list
    .iter()
    // No Error
    .map(|x| get_proverb_part(x))
    // Error
    //.map(get_proverb_part)
    .collect::<Vec<&str>>()
    .join("\n")
}

fn get_proverb_part(keyword: &str) -> &str {
  ""
}