}
    }

    private static <T> T cache(ModelCache cache, Source source, String tag, Callable<T> supplier) {
        Supplier<T> s = asSupplier(supplier);
        if (cache == null) {
            return s.get();
        } else {
            return cache.computeIfAbsent(source, tag, s);
        }
    }

    private static <T> Supplier<T> asSupplier(Callable<T> supplier) {

            throw new IllegalArgumentException("reader or inputStream must be non null");
        }
        try {
            InputSource source = null;
            if (request.getModelId() != null || request.getLocation() != null) {
                source = new InputSource(request.getModelId(), request.getLocation());
            }
            MavenToolchainsStaxReader xml = new MavenToolchainsStaxReader();

            throw new IllegalArgumentException("reader or inputStream must be non null");
        }
        try {
            InputSource source = null;
            if (request.getModelId() != null || request.getLocation() != null) {
                source = new InputSource(request.getModelId(), request.getLocation());
            }
            MavenToolchainsStaxReader xml = new MavenToolchainsStaxReader();

                ModelSource source = getSource(groupId, artifactId);
                if (source == null) {
                    // we need to check the whole reactor in case it's a dependency
                    loadFullReactor();
                    source = getSource(groupId, artifactId);
                }
                if (source != null) {
                    if (!addEdge(from, source.getPath(), problems)) {

    }

    /**
     * DuplicateMerger
     */
    protected static class DuplicateMerger extends MavenModelMerger {

        public Plugin mergePlugin(Plugin target, Plugin source) {
            return super.mergePlugin(target, source, false, Collections.emptyMap());
        }
    }

    @Override
    public Model injectDefaultValues(Model model, ModelBuilderRequest request, ModelProblemCollector problems) {

            }

            return null;
        }
    }

    /**
     * Wraps an arbitrary object with an {@link ObjectBasedValueSource} instance, then
     * wraps that source with a {@link PrefixedValueSourceWrapper} instance, to which
     * this class delegates all of its calls.
     */
    public static class PrefixedObjectValueSource extends AbstractDelegatingValueSource

    private static final String[] PHASES = {
        "validate",
        "initialize",
        "generate-sources",
        "process-sources",
        "generate-resources",
        "process-resources",
        "compile",
        "process-classes",
        "generate-test-sources",
        "process-test-sources",
        "generate-test-resources",
        "process-test-resources",
        "test-compile",

    Object getConfiguration();

    /**
     * Sets the configuration to unmarshal into the bean. The configuration should be taken from
     * {@link org.apache.maven.model.ConfigurationContainer#getConfiguration()} or a similar source.
     * Fully equivalent to {@code setConfiguration(configuration, null)}.
     *
     * @param configuration The configuration to unmarshal, may be {@code null}.
     * @return This request for chaining, never {@code null}.

    </dependency>
  </dependencies>

  <build>
    <resources>
      <resource>
        <directory>.</directory>
        <includes>
          <include>pom.xml</include>
          <include>src/**</include>
        </includes>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
      </resource>
    </resources>
  </build>

    </dependency>
  </dependencies>

  <build>
    <resources>
      <resource>
        <directory>.</directory>
        <includes>
          <include>pom.xml</include>
          <include>src/**</include>
        </includes>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
      </resource>
    </resources>
  </build>