@Nonnull
            @Override
            public Optional<Project> getProject() {
                return Optional.ofNullable(project);
            }

            @Nonnull
            @Override
            public Optional<Artifact> getRootArtifact() {
                return Optional.ofNullable(rootArtifact);
            }

            @Nonnull
            @Override

    }

    private Optional<String> extractRequiredJavaVersion(PlexusConfiguration c) {
        return Optional.ofNullable(c.getChild("requiredJavaVersion")).map(PlexusConfiguration::getValue);
    }

    private Optional<String> extractRequiredMavenVersion(PlexusConfiguration c) {
        return Optional.ofNullable(c.getChild("requiredMavenVersion")).map(PlexusConfiguration::getValue);
    }

    }

    public OptionalEntity<WebConfig> getWebConfig() {
        return OptionalUtil.ofNullable(webConfig);
    }

    public OptionalEntity<FileConfig> getFileConfig() {
        return OptionalUtil.ofNullable(fileConfig);
    }

    public LabelType[] getLabelTypes() {
        return labelList.toArray(new LabelType[labelList.size()]);
    }

        if (artifact == null) {
            return null;
        }

        Artifact result = toArtifact(artifact);

        List<Exclusion> excl = Optional.ofNullable(exclusions).orElse(Collections.emptyList()).stream()
                .map(RepositoryUtils::toExclusion)
                .collect(Collectors.toList());

     *
     * @return the {@code javax.tool} enumeration value corresponding to this {@code JavaPathType}
     */
    public Optional<JavaFileManager.Location> location() {
        return Optional.ofNullable(location);
    }

    /**
     * Returns the path type associated to the given {@code javax.tool} location.
     * This method is the converse of {@link #location()}.
     *

   * reference; otherwise returns {@link Optional#absent}.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's
   * {@code Optional.ofNullable}.
   */
  public static <T> Optional<T> fromNullable(@CheckForNull T nullableReference) {
    return (nullableReference == null) ? Optional.<T>absent() : new Present<T>(nullableReference);
  }

  /**

        return incidentNodes(edge).adjacentNode(nodePresent).equals(nodeToCheck);
      }
    };
  }

  @Override
  public Optional<E> edgeConnecting(N nodeU, N nodeV) {
    return Optional.ofNullable(edgeConnectingOrNull(nodeU, nodeV));
  }

  @Override
  public Optional<E> edgeConnecting(EndpointPair<N> endpoints) {
    validateEndpoints(endpoints);

                private final Map<Artifact, Path> paths = new ConcurrentHashMap<>();

                @Override
                public Optional<Path> getPath(Artifact artifact) {
                    return Optional.ofNullable(paths.get(artifact));
                }

                @Override
                public void setPath(ProducedArtifact artifact, Path path) {
                    paths.put(artifact, path);
                }