}

  @Override
  public Set<N> adjacentNodes(N node) {
    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public Set<E> incidentEdges(N node) {
    return delegate().incidentEdges(node);
  }

        case Node.ELEMENT_NODE:
            appendElement((Element) node, buf);
            break;
        case Node.TEXT_NODE:
            appendText((Text) node, buf);
            break;
        case Node.CDATA_SECTION_NODE:
            appendCDATASection((CDATASection) node, buf);
            break;
        case Node.ENTITY_REFERENCE_NODE:
            appendEntityReference((EntityReference) node, buf);

            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;
    }

    if (predecessors != null) {
      checkState(predecessors.remove(node));
    }
    return node;
  }

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

  @Override

    if (predecessors != null) {
      checkState(predecessors.remove(node));
    }
    return node;
  }

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

  @Override

      node = root.ceiling(comparator(), endpoint);
      if (node == null) {
        return null;
      }
      if (range.getLowerBoundType() == BoundType.OPEN
          && comparator().compare(endpoint, node.getElement()) == 0) {
        node = node.succ();
      }
    } else {
      node = header.succ();
    }
    return (node == header || !range.contains(node.getElement())) ? null : node;
  }

                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
     */

  /**
   * 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> {

  @CanIgnoreReturnValue
  N removeOutEdge(E edge);

  /**
   * Add {@code edge} to the set of incoming edges. Implicitly adds {@code node} as a predecessor.
   */
  void addInEdge(E edge, N node, boolean isSelfLoop);

  /** Add {@code edge} to the set of outgoing edges. Implicitly adds {@code node} as a successor. */
  void addOutEdge(E edge, N node);

     * @return the parsed XML node
     * @throws XMLStreamException if there is an error parsing the XML
     */
    protected abstract XmlNode doRead(XMLStreamReader reader, InputLocationBuilder locationBuilder)
            throws XMLStreamException;

    /**
     * Implementation method for writing an XML node to a writer.
     *
     * @param node the XML node to write
     * @param writer the writer to write to