/**
   * Removes the edge connecting {@code endpoints}, if it is present.
   *
   * <p>If this graph is directed, {@code endpoints} must be ordered.
   *
   * @return the value previously associated with the edge connecting {@code endpoints}, or null if
   *     there was no such edge.
   * @since 27.1
   */
  @CanIgnoreReturnValue
  @Nullable V removeEdge(EndpointPair<N> endpoints);

    /**
     * Adds an edge connecting {@code endpoints} (in the order, if any, specified by {@code
     * endpoints}) if one is not already present.
     *
     * <p>If this graph is directed, {@code endpoints} must be ordered and the added edge will be
     * directed; if it is undirected, the added edge will be undirected.
     *
     * <p>If this graph is directed, {@code endpoints} must be ordered.
     *

     * must also be non-null.
     *
     * <p>If either or both endpoints are not already present in this network, this method will
     * silently {@link #addNode(Object) add} each missing endpoint to the network.
     *
     * <p>If {@code edge} already connects an endpoint pair equal to {@code endpoints}, then this
     * method will have no effect.
     *
     * @return this {@code Builder} object

  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    return isOrderingCompatible(endpoints)
        && hasEdgeConnectingInternal(endpoints.nodeU(), endpoints.nodeV());
  }

  @Override
  public @Nullable V edgeValueOrDefault(N nodeU, N nodeV, @Nullable V defaultValue) {

  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    if (!isOrderingCompatible(endpoints)) {
      return false;
    }
    return hasEdgeConnecting(endpoints.nodeU(), endpoints.nodeV());
  }

  /**
   * Throws an IllegalArgumentException if the ordering of {@code endpoints} is not compatible with
   * the directionality of this graph.
   */

   * Returns the value of the edge that connects {@code endpoints} (in the order, if any, specified
   * by {@code endpoints}), if one is present; otherwise, returns {@code defaultValue}.
   *
   * <p>If this graph is directed, the endpoints must be ordered.
   *
   * @throws IllegalArgumentException if either endpoint is not an element of this graph
   * @throws IllegalArgumentException if the endpoints are unordered and the graph is directed

   * also be non-null.
   *
   * <p>If either or both endpoints are not already present in this graph, this method will silently
   * {@link #addNode(Object) add} each missing endpoint to the graph.
   *
   * <p>If {@code edge} already connects an endpoint pair equal to {@code endpoints}, then this
   * method will have no effect.
   *

  /**
   * Adds an edge connecting {@code endpoints} (in the order, if any, specified by {@code
   * endpoints}) if one is not already present.
   *
   * <p>If this graph is directed, {@code endpoints} must be ordered and the added edge will be
   * directed; if it is undirected, the added edge will be undirected.
   *
   * <p>If this graph is directed, {@code endpoints} must be ordered.
   *

   * order, if any, specified by {@code endpoints}).
   *
   * <p>The resulting set of edges will be parallel (i.e. have equal {@link
   * #incidentNodes(Object)}). If this network does not {@link #allowsParallelEdges() allow parallel
   * edges}, the resulting set will contain at most one edge (equivalent to {@code
   * edgeConnecting(endpoints).asSet()}).
   *

     *
     * <p>If either or both endpoints are not already present in this graph, this method will
     * silently {@link #addNode(Object) add} each missing endpoint to the graph.
     *
     * @return this {@code Builder} object
     * @throws IllegalArgumentException if the introduction of the edge would violate {@link
     *     #allowsSelfLoops()}
     * @throws IllegalArgumentException if the endpoints are unordered and the graph is directed