@SuppressWarnings("CheckReturnValue")
  private ImmutableSet<N> validate(Iterable<? extends N> startNodes) {
    ImmutableSet<N> copy = ImmutableSet.copyOf(startNodes);
    for (N node : copy) {
      successorFunction.successors(node); // Will throw if node doesn't exist
    }
    return copy;
  }

  /**
   * Abstracts away the difference between traversing a graph vs. a tree. For a tree, we just take

    for (int size = 2; size < 16; size++) {
      for (int attempts = 0; attempts < size * (size - 1); attempts++) {
        ArrayList<Integer> elements = createOrderedList(size);
        List<Integer> expected = ImmutableList.copyOf(elements);
        MinMaxPriorityQueue<Integer> q = MinMaxPriorityQueue.create();
        long seed = insertRandomly(elements, q);
        while (!q.isEmpty()) {
          elements.add(q.pollFirst());
        }

                  @Override
                  protected Set<String> create(String[] elements) {
                    Table<String, Integer, Character> table =
                        ArrayTable.create(ImmutableList.copyOf(elements), ImmutableList.of(1, 2));
                    populateForRowKeySet(table, elements);
                    return table.rowKeySet();
                  }
                })

   * the current capacity.
   */
  void resizeEntries(int newCapacity) {
    this.entries = Arrays.copyOf(requireEntries(), newCapacity);
    this.elements = Arrays.copyOf(requireElements(), newCapacity);
  }

  @CanIgnoreReturnValue
  private int resizeTable(int oldMask, int newCapacity, int targetHash, int targetEntryIndex) {

                  @Override
                  protected Set<String> create(String[] elements) {
                    Table<String, Integer, Character> table =
                        ArrayTable.create(ImmutableList.copyOf(elements), ImmutableList.of(1, 2));
                    populateForRowKeySet(table, elements);
                    return table.rowKeySet();
                  }
                })

  }

  @Test
  public void addEdge_existingEdgeBetweenSameNodes() {
    assume().that(graphIsMutable()).isTrue();

    addEdge(N1, N2, E12);
    ImmutableSet<String> edges = ImmutableSet.copyOf(network.edges());
    assertThat(networkAsMutableNetwork.addEdge(N1, N2, E12)).isFalse();
    assertThat(network.edges()).containsExactlyElementsIn(edges);
  }

  @Test

        put(cell.getRowKey(), cell.getColumnKey(), cell.getValue(), merger);
      }
      return this;
    }

    ImmutableTable<R, C, V> toTable() {
      return ImmutableTable.copyOf(insertionOrder);
    }
  }

  @IgnoreJRERequirement // see enclosing class (whose annotation Animal Sniffer ignores here...)
  private static final class MutableCell<R, C, V> extends AbstractCell<R, C, V> {

 * you should use the non-mutating {@link Graph} interface, or an {@link ImmutableGraph}.
 *
 * <p>You can create an immutable copy of an existing {@code Graph} using {@link
 * ImmutableGraph#copyOf(Graph)}:
 *
 * {@snippet :
 * ImmutableGraph<Integer> immutableGraph = ImmutableGraph.copyOf(graph);
 * }
 *
 * <p>Instances of {@link ImmutableGraph} do not implement {@link MutableGraph} (obviously!) and are

              @Override
              public Set<AnEnum> create(AnEnum[] elements) {
                return (elements.length == 0)
                    ? EnumSet.noneOf(AnEnum.class)
                    : EnumSet.copyOf(MinimalCollection.of(elements));
              }
            })
        .named("EnumSet")
        .withFeatures(
            SetFeature.GENERAL_PURPOSE,
            CollectionFeature.SERIALIZABLE,

        K castKey = (K) key;
        V value = getIfPresent(key);
        if (value != null) {
          result.put(castKey, value);
        }
      }
    }
    return ImmutableMap.copyOf(result);
  }

  /**
   * @since 11.0
   */
  @Override
  public void put(K key, V value) {
    throw new UnsupportedOperationException();
  }

  /**
   * @since 12.0
   */
  @Override