/**
   * 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.
   *

  }

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

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

    assume().that(graphIsMutable()).isTrue();

    EndpointPair<Integer> endpoints = EndpointPair.ordered(N1, N2);
    IllegalArgumentException e =
        assertThrows(
            IllegalArgumentException.class, () -> networkAsMutableNetwork.addEdge(endpoints, E12));
    assertThat(e).hasMessageThat().contains(ENDPOINTS_MISMATCH);
  }

  @Test
  public void addEdge_selfLoop_notAllowed() {

   * 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()}).
   *

    }

    /**
     * Adds an edge connecting {@code endpoints} if one is not already present, and sets a value for
     * that edge to {@code value} (overwriting the existing value, if any).
     *
     * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
     * undirected.
     *
     * <p>If this graph is directed, {@code endpoints} must be ordered.
     *

  /**
   * Returns true if there is an edge that directly connects {@code endpoints} (in the order, if
   * any, specified by {@code endpoints}). This is equivalent to {@code
   * edges().contains(endpoints)}.
   *
   * <p>Unlike the other {@code EndpointPair}-accepting methods, this method does not throw if the
   * endpoints are unordered; it simply returns false. This is for consistency with the behavior of

  /**
   * Returns true if there is an edge that directly connects {@code endpoints} (in the order, if
   * any, specified by {@code endpoints}). This is equivalent to {@code
   * edges().contains(endpoints)}.
   *
   * <p>Unlike the other {@code EndpointPair}-accepting methods, this method does not throw if the
   * endpoints are unordered and the graph is directed; it simply returns {@code false}. This is for

    return create(Range.closed(lower, upper), DiscreteDomain.longs());
  }

  /**
   * Returns a contiguous set containing all {@code int} values from {@code lower} (inclusive) to
   * {@code upper} (exclusive). If the endpoints are equal, an empty set is returned. (These are the
   * same values contained in {@code Range.closedOpen(lower, upper)}.)
   *
   * @throws IllegalArgumentException if {@code lower} is greater than {@code upper}

    return new GeneralRange<>(comparator, false, null, OPEN, true, endpoint, boundType);
  }

  /**
   * Returns everything between the endpoints relative to the specified comparator, with the
   * specified endpoint behavior.
   */
  static <T extends @Nullable Object> GeneralRange<T> range(
      Comparator<? super T> comparator,
      @ParametricNullness T lower,

  }

  @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.
   */