private void validateListMapSetShapes(Shape shape, PathFinder finder, List<ValidationEvent> events) {
        for (PathFinder.Path path : finder.search(shape, Collections.singletonList(shape))) {
            events.add(error(shape,
                    String.format(
                            "Found invalid shape recursion: %s. A recursive list, set, or map shape is only "
                                    + "valid if an intermediate reference is through a union or structure.",
                            formatPath(path))));
        }
    }
Ensures that list, set, and map shapes are not directly recursive,
meaning that if they do have a recursive reference to themselves,
one or more references that form the recursive path travels through
a structure or union shape. And ensures that structure members are
not infinitely mutually recursive using the required trait.

<p>This check removes an entire class of problems from things like
code generators where a list of itself or a list of maps of itself
is impossible to define.
smithy-model/src/main/java/software/amazon/smithy/model/validation/validators/ShapeRecursionValidator.java