@Override
    public Response push(Context context, Shape shape, Receiver next) {
        // Some internal selectors provide optimizations for quickly checking if they contain a shape.
        switch (selector.containsShapeOptimization(context, shape)) {
            case YES:
                return next.apply(context, shape);
            case NO:
                return Response.CONTINUE;
            case MAYBE:
            default:
                // Unable to use the optimization, so emit each shape until a match is found.
                FilteredHolder holder = new FilteredHolder(shape);
                selector.push(context, shape, holder);

                if (holder.matched) {
                    return next.apply(context, shape);
                }

                return Response.CONTINUE;
        }
    }
Checks if the given value is in the result of a selector.
smithy-model/src/main/java/software/amazon/smithy/model/selector/InSelector.java