pub trait Parser: Send + Sync {
    // Required method
    fn parse<'a>(
        &self,
        registry: &ParserRegistry,
        input: &'a str,
    ) -> ParseResult<'a>;
    // Provided method
    fn extend(&self, parser: ParserHandle) { ... }
}pub trait Parser: Send + Sync {
    // Required method
    fn parse<'a>(
        &self,
        registry: &ParserRegistry,
        input: &'a str,
    ) -> ParseResult<'a>;
    // Provided method
    fn extend(&self, parser: ParserHandle) { ... }
}