Model model = loadPom(session, request, result);
        if (model != null) {
            Map<String, Object> config = session.getConfigProperties();
            ArtifactDescriptorReaderDelegate delegate =
                    (ArtifactDescriptorReaderDelegate) config.get(ArtifactDescriptorReaderDelegate.class.getName());

            if (delegate == null) {
                delegate = this.delegate;

          BinaryOperator<V> mergeFunction) {
    return CollectCollectors.toImmutableSortedMap(
        comparator, keyFunction, valueFunction, mergeFunction);
  }

  /*
   * TODO(kevinb): Confirm that ImmutableSortedMap is faster to construct and
   * uses less memory than TreeMap; then say so in the class Javadoc.
   */
  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();