*
   * @return the value previously associated with the edge connecting {@code nodeU} to {@code
   *     nodeV}, or null if there was no such edge.
   * @throws IllegalArgumentException if the introduction of the edge would violate {@link
   *     #allowsSelfLoops()}
   */
  @CanIgnoreReturnValue
  @Nullable V putEdgeValue(N nodeU, N nodeV, V value);

  /**

     * silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the graph.
     *
     * @return this {@code Builder} object
     * @throws IllegalArgumentException if the introduction of the edge would violate {@link
     *     #allowsSelfLoops()}
     */
    @CanIgnoreReturnValue
    public ImmutableValueGraph.Builder<N, V> putEdgeValue(N nodeU, N nodeV, V value) {
      mutableValueGraph.putEdgeValue(nodeU, nodeV, value);

   *
   * @return {@code true} if the graph was modified as a result of this call
   * @throws IllegalArgumentException if the introduction of the edge would violate {@link
   *     #allowsSelfLoops()}
   */
  @CanIgnoreReturnValue
  boolean putEdge(N nodeU, N nodeV);

  /**
   * Adds an edge connecting {@code endpoints} (in the order, if any, specified by {@code

 * elements, if there is no comparator) to test element equality. As a result, if the comparator is
 * not consistent with equals, some of the standard implementations may violate the {@code Set}
 * contract.
 *
 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *

 * elements, if there is no comparator) to test element equality. As a result, if the comparator is
 * not consistent with equals, some of the standard implementations may violate the {@code Set}
 * contract.
 *
 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *

   * level than the whole method but without performing a runtime null check. That way, we can still
   * pass null inputs to LegacyConverter, and it can violate the contract of Converter.
   *
   * TODO(cpovirk): Could this be simplified if we modified implementations of LegacyConverter to
   * override methods (probably called "unsafeDoForward" and "unsafeDoBackward") with the same

   * Returns -1 if no further cleanups are required.
   */
  fun closeConnections(now: Long): Long {
    // Compute the concurrent call capacity for each address. We won't close a connection if doing
    // so would violate a policy, unless it's OLD.
    val addressStates = this.addressStates
    for (state in addressStates.values) {
      state.concurrentCallCapacity = 0
    }
    for (connection in connections) {

 * elements, if there is no comparator) to test element equality. As a result, if the comparator is
 * not consistent with equals, some of the standard implementations may violate the {@code Map}
 * contract.
 *
 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *

 * elements, if there is no comparator) to test element equality. As a result, if the comparator is
 * not consistent with equals, some of the standard implementations may violate the {@code Map}
 * contract.
 *
 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *

   *
   * <p><b>Warning:</b> when this method is used, the resulting cache will use identity ({@code ==})
   * comparison to determine equality of keys. Its {@link Cache#asMap} view will therefore
   * technically violate the {@link Map} specification (in the same way that {@link IdentityHashMap}
   * does).
   *
   * <p>Entries with keys that have been garbage collected may be counted in {@link Cache#size}, but