PluginExecution existing = merged.get(key);
                    if (existing != null) {
                        element = mergePluginExecution(existing, element, sourceDominant, context);
                    }
                    merged.put(key, element);
                }

                builder.executions(merged.values());
            }
        }

        @Override

import org.apache.maven.api.services.model.*;

/**
 * Handles normalization of a model.
 *
 */
@Named
@Singleton
public class DefaultModelNormalizer implements ModelNormalizer {

    private DuplicateMerger merger = new DuplicateMerger();

    @Override
    public Model mergeDuplicates(Model model, ModelBuilderRequest request, ModelProblemCollector problems) {
        Model.Builder builder = Model.newBuilder(model);

                        .artifactId(pluginInfo.artifactId)
                        .name(pluginInfo.name)
                        .build()))
                .build();
    }

    @Override
    protected void merge(Metadata recessive) {
        List<Plugin> recessivePlugins = recessive.getPlugins();
        List<Plugin> plugins = metadata.getPlugins();
        if (!recessivePlugins.isEmpty() || !plugins.isEmpty()) {

    @Nullable
    Object getInputLocation();

    default XmlNode merge(@Nullable XmlNode source) {
        return merge(source, (Boolean) null);
    }

    XmlNode merge(@Nullable XmlNode source, @Nullable Boolean childMergeOverride);

    /**
     * Merge recessive into dominant and return either {@code dominant}
     * with merged information or a clone of {@code recessive} if
     * {@code dominant} is {@code null}.

            versioning.latest(artifact.getBaseVersion());
        }

        metadata.versioning(versioning.build());

        return metadata.build();
    }

    @Override
    protected void merge(Metadata recessive) {
        Versioning original = metadata.getVersioning();

        Versioning.Builder versioning = Versioning.newBuilder(original);
        versioning.lastUpdated(fmt.format(timestamp));

        Settings recessive = Settings.newBuilder()
                .pluginGroups(Arrays.asList("org.codehaus.plexus"))
                .build();

        Settings merged = SettingsUtilsV4.merge(dominant, recessive);

        List<String> pluginGroups = merged.getPluginGroups();

        assertNotNull(pluginGroups);
        assertEquals(3, pluginGroups.size());
        assertEquals("org.apache.maven.plugins", pluginGroups.get(0));

        Source userSource = request.getUserToolchainsSource().orElse(null);
        PersistedToolchains user = readToolchains(userSource, request, problems);

        PersistedToolchains effective = toolchainsMerger.merge(user, global, false, null);

        if (hasErrors(problems)) {
            throw new ToolchainsBuilderException("Error building toolchains", problems);
        }

                    PluginExecution existing = merged.get(key);
                    if (existing != null) {
                        element = mergePluginExecution(element, existing, sourceDominant, context);
                    }
                    merged.put(key, element);
                }

                builder.executions(merged.values());
            }
        }
    }

                    .build();
            model.update(merger.merge(model.getDelegate(), lifecycleModel));
        }
    }

    /**
     *  The domain-specific model merger for lifecycle bindings
     */
    protected static class LifecycleBindingsMerger extends MavenModelMerger {

        private static final String PLUGIN_MANAGEMENT = "plugin-management";

        public Model merge(Model target, Model source) {

 *
 */
public interface ModelNormalizer {

    /**
     * Merges duplicate elements like multiple declarations of the same build plugin in the specified model.
     *
     * @param model The model whose duplicate elements should be merged, must not be {@code null}.
     * @param request The model building request that holds further settings, must not be {@code null}.