*
   * <p>The default value is {@code false}.
   */
  @CanIgnoreReturnValue
  public NetworkBuilder<N, E> allowsParallelEdges(boolean allowsParallelEdges) {
    this.allowsParallelEdges = allowsParallelEdges;
    return this;
  }

  /**
   * Specifies whether the network will allow self-loops (edges that connect a node to itself).

      NetworkBuilder<? super N, ? super E> builder,
      Map<N, NetworkConnections<N, E>> nodeConnections,
      Map<E, N> edgeToReferenceNode) {
    this.isDirected = builder.directed;
    this.allowsParallelEdges = builder.allowsParallelEdges;
    this.allowsSelfLoops = builder.allowsSelfLoops;
    this.nodeOrder = builder.nodeOrder.cast();
    this.edgeOrder = builder.edgeOrder.cast();