Optional GROUP BY statement

[Kimishu]

Working on my custom sql validation, I needed somehow to check, does user provide group_by/limit+offset/sort_by clauses.
I got smth like this and found .group_by field as non-optional. Is it right?

let wrong_query = "SELECT * FROM example_table GROUP BY example_field";
//Parser returns success(!) below
if let Statement::Query(q) = Parser::parse_sql(&GenericDialect {}, &query)?.first().unwrap() {
     if q.limit_clause.is_none() {...}
     if q.order_by.is_none() {...}
     let select_query = query.body.as_select().unwrap();
     //And I expected smth like this:
     if select_query.group_by.is_none() {...}
}

Maybe I'm doing smth wrong and there is a proper and faster way for that?
Also I noticed a parse_optional_group_by fn but I didn't get how to use it., there is no info nor examples in docs about it. Looks like it's inner fn?