static Function<TreeCursor, Stream<Doc>> extractor(
            Function<TreeCursor, Doc> visitor,
            Function<TreeCursor, Stream<TreeCursor>> mapper
    ) {
        return extractor(visitor, mapper, TreeCursor::children);
    }
Formats various kinds of brackets, dealing with interspersed whitespace and comments.
smithy-syntax/src/main/java/software/amazon/smithy/syntax/BracketFormatter.java