Function render_rule 

pub fn render_rule(
    grammar_json: &str,
    name: &str,
) -> Result<String, GrammarError>

Render a single production’s right-hand side (display names applied), exactly as it appears after <name> ::= in the appendix’s EBNF block.

Errors if the grammar JSON cannot be parsed, or if name is not a top-level rule of the grammar.