// attribute that doesn't have a precedence
                (Attribute.of("z", String)): "z"
        )

        then:
        def result = schema.withProducer(producer).selectionSchema.orderByPrecedence(requested.keySet())
        result.sortedOrder == [2, 1, 0]
        result.unsortedOrder as List == [3]
    }

     *
     * @param requested The attributes to order. <strong>Must have a consistent iteration ordering and cannot contain duplicates</strong>.
     *
     * @return The ordered attributes.
     */
    PrecedenceResult orderByPrecedence(Collection<Attribute<?>> requested);

        // The sorted indices are [ 2, 0 ]
        // The unsorted indices are [ 1 ]
        //
        final AttributeSelectionSchema.PrecedenceResult precedenceResult = schema.orderByPrecedence(requested.keySet());

        for (int a : precedenceResult.getSortedOrder()) {
            disambiguateRequestedAttribute(a);
            if (remaining.cardinality() == 0) {
                return;

                AttributeSelectionUtils.collectExtraAttributes(this, candidateAttributeSets, requested));
        }

        @Override
        public PrecedenceResult orderByPrecedence(Collection<Attribute<?>> requested) {
            if (consumerSchema.getAttributeDisambiguationPrecedence().isEmpty() && producerSchema.getAttributeDisambiguationPrecedence().isEmpty()) {

            AttributeSelectionUtils.collectExtraAttributes(this, candidates, requested)
        }

        @Override
        PrecedenceResult orderByPrecedence(Collection<Attribute<?>> requested) {
            return new PrecedenceResult(IntStream.range(0, requested.size()).boxed().collect(Collectors.toList()))
        }
    }