String value = transformer.getSingleNodeValue(document, "//BODY", node -> node);
        assertEquals("aaa", value);

        value = transformer.getSingleNodeValue(document, "//META[@name='keywords']/@content", node -> node);
        assertEquals("bbb", value);

        value = transformer.getSingleNodeValue(document, "//META[@name='keywords']/@content|//BODY", node -> node);
        assertEquals("bbb aaa", value);
    }

                ids.add(0, artifact);
                node = node.parent;
            }
            trail = ids;
        }
        return trail;
    }

    public boolean isResolved() {
        return children != null;
    }

    /**
     * Test whether the node is direct or transitive dependency.
     *
     * @return whether the node is direct or transitive dependency
     */

            MetadataTreeNode node = new MetadataTreeNode(md, parent, md.isResolved(), md.getArtifactScope());
            if (tree == null) {
                tree = node;
            }

            if (parent != null) {
                parent.setNChildren(1);
                parent.addChild(0, node);
            }

            parent = node;
        }
        return tree;
    }

 * with user-defined properties.
 *
 * <p>A {@code ValueGraph} built by this class has the following default properties:
 *
 * <ul>
 *   <li>does not allow self-loops
 *   <li>orders {@link ValueGraph#nodes()} in the order in which the elements were added (insertion
 *       order)
 * </ul>
 *
 * <p>{@code ValueGraph}s built by this class also guarantee that each collection-returning accessor

        protected void visit(MetadataGraphVertex node) {
            ArtifactMetadata md = node.getMd();
            if (visited.contains(node)) {
                return;
            }

            cpc.add(md);

            List<MetadataGraphEdge> exits = graph.getExcidentEdges(node);

            if (exits != null && !exits.isEmpty()) {

        public Node insertBefore(Node newChild, Node refChild) {
            return null;
        }

        @Override
        public Node replaceChild(Node newChild, Node oldChild) {
            return null;
        }

        @Override
        public Node removeChild(Node oldChild) {
            return null;
        }

        @Override
        public Node appendChild(Node newChild) {

    void omitForCycle(Artifact artifact);

    /**
     * This event means that the artifactScope has NOT been updated to a farther node artifactScope because current
     * node is in the first level pom
     *
     * @param artifact     current node artifact, the one in the first level pom
     * @param ignoredScope artifactScope that was ignored because artifact was in first level pom
     */

  public N removeOutEdge(E edge) {
    N node = super.removeOutEdge(edge);
    Multiset<N> adjacentNodes = getReference(adjacentNodesReference);
    if (adjacentNodes != null) {
      checkState(adjacentNodes.remove(node));
    }
    return node;
  }

  @Override
  public void addInEdge(E edge, N node, boolean isSelfLoop) {
    if (!isSelfLoop) {
      addOutEdge(edge, node);
    }
  }

  @Override

  /**
   * A value class representing single connection between the origin node and another node.
   *
   * <p>There can be two types of connections (predecessor and successor), which is represented by
   * the two implementations.
   */
  private abstract static class NodeConnection<N> {
    final N node;

    NodeConnection(N node) {
      this.node = checkNotNull(node);
    }

    static final class Pred<N> extends NodeConnection<N> {

  }

  @Override
  public @Nullable V value(N node) {
    return adjacentNodeValues.get(node);
  }

  @Override
  public void removePredecessor(N node) {
    @SuppressWarnings("unused")
    V unused = removeSuccessor(node);
  }

  @Override
  public @Nullable V removeSuccessor(N node) {
    return adjacentNodeValues.remove(node);
  }

  @Override