Function write_entry 

fn write_entry(
    output: &mut String,
    is_term: bool,
    id: &Identifier<String>,
    value: Option<&Pattern<String>>,
    attributes: &[Attribute<String>],
    filter: &dyn Fn(&str, &str) -> bool,
    transform: &dyn Fn(&str) -> Cow<'_, str>,
)