*/
    <T> void set(@Nonnull Key<T> key, @Nullable T value);

    /**
     * Associates the specified session data with the given key if the key is currently mapped to the given value. This
     * method provides an atomic compare-and-update of some key's value.
     *
     * @param key the key under which to store the session data, must not be {@code null}

    public String getId() {
        StringBuilder id = new StringBuilder( 64 );

        id.append( ( getGroupId() == null ) ? "[inherited]" : getGroupId() );
        id.append( ":" );
        id.append( getArtifactId() );
        id.append( ":" );
        id.append( getPackaging() );
        id.append( ":" );
        id.append( ( getVersion() == null ) ? "[inherited]" : getVersion() );

        return id.toString();
    }

        StringBuilder sb = new StringBuilder(128);
        sb.append("MavenProject: ");
        sb.append(getGroupId());
        sb.append(':');
        sb.append(getArtifactId());
        sb.append(':');
        sb.append(getVersion());
        if (getFile() != null) {
            sb.append(" @ ");
            sb.append(getFile().getPath());
        }

        return sb.toString();
    }

            buffer.append("'parent.relativePath'");
            if (childModel != problems.getRootModel()) {
                buffer.append(" of POM ").append(ModelProblemUtils.toSourceHint(childModel));
            }
            buffer.append(" points at ").append(groupId).append(':').append(artifactId);
            buffer.append(" instead of ").append(parent.getGroupId()).append(':');

            result.add(executionPlanItem.getMojoExecution());
        }
        return result;
    }

    /**
     * Get set of plugins having a goal/mojo used but not marked @threadSafe
     *
     * @return the set of plugins (without info on which goal is concerned)
     */
    public Set<Plugin> getNonThreadSafePlugins() {
        Set<Plugin> plugins = new HashSet<>();

            // The root locator can be used very early during the setup of Maven,
            // even before the arguments from the command line are parsed.  Any exception
            // that would happen here should cause the build to fail at a later stage
            // (when actually parsing the POM) and will lead to a better exception being
            // displayed to the user, so just bail out and return false.
        }

    }

    private static String createPath(List<String> elements) {
        StringBuilder buffer = new StringBuilder(256);
        for (String s : elements) {
            buffer.append(s).append(File.separator);
        }
        return buffer.toString().substring(0, buffer.toString().length() - 1);
    }

@Experimental
@ThreadSafe
@Immutable
public interface XmlNode {

    String CHILDREN_COMBINATION_MODE_ATTRIBUTE = "combine.children";

    String CHILDREN_COMBINATION_MERGE = "merge";

    String CHILDREN_COMBINATION_APPEND = "append";

    /**
     * This default mode for combining children DOMs during merge means that where element names match, the process will

        buffer.append("<?xml version='1.0'?>");
        buffer.append("<project>");
        buffer.append("<modelVersion>4.0.0</modelVersion>");
        buffer.append("<groupId>").append(artifact.getGroupId()).append("</groupId>");
        buffer.append("<artifactId>").append(artifact.getArtifactId()).append("</artifactId>");
        buffer.append("<version>").append(artifact.getBaseVersion()).append("</version>");

        }
        return clazz.cast(o);
    }

    static <U, V> List<V> map(Collection<U> list, Function<U, V> mapper) {
        return list.stream().map(mapper).collect(Collectors.toList());
    }