public Set<Shape> getOrderedShapes() {
        return Collections.unmodifiableSet(shapes);
    }
Gets all reverse-topologically ordered shapes, including members.

<p>When the returned {@code Set} is iterated, shapes are returned in
reverse-topological. Note that the returned set does not contain
recursive shapes.

@return Non-recursive shapes in a reverse-topological ordered {@code Set}.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/TopologicalIndex.java