Function format_entry 

fn format_entry(key: &str, entry: &BibEntry) -> String

Render one BibTeX entry as plain text for the bibliography list.

Not a CSL processor: a fixed Author. Title. Venue, volume, pp. pages. Publisher. Year. order where every missing field simply drops out. Brace protection is stripped and whitespace collapsed via clean_field; a part that already ends in . (initials like Knuth, D. E.) is not double-terminated. An entry with no usable fields falls back to its citation key so a numbered slot never renders empty.