* #iterator()} method after the first, and whose iterator is always unmodifiable.
 *
 * <p>The {@code Iterable} specification does not make it absolutely clear what should happen on a
 * second invocation, so implementors have made various choices, including:
 *
 * <ul>
 *   <li>returning the same iterator again
 *   <li>throwing an exception of some kind
 *   <li>or the usual, <i>robust</i> behavior, which all known {@link Collection} implementations

 * java.util.function.Predicate} is expected, use the method reference {@code
 * guavaPredicate::apply}. For the other direction, use {@code javaUtilPredicate::test}. A future
 * version of this interface will be made to <i>extend</i> {@code java.util.function.Predicate}, so
 * that conversion will be necessary in only one direction. At that time, this interface will be
 * officially discouraged.
 *
 * @author Kevin Bourrillion

    return result;
  }

  /*
   * Memory visibility of these fields. There are two cases to consider.
   *
   * 1. visibility of the writes to these fields to Fire.run:
   *
   * The initial write to delegateRef is made definitely visible via the semantics of
   * addListener/SES.schedule. The later racy write in cancel() is not guaranteed to be observed,
   * however that is fine since the correctness is based on the atomic state in our base class. The

 * <i>other type</i> of supplier is expected, use the method reference {@code supplier::get}. A
 * future version of {@code com.google.common.base.Supplier} will be made to <i>extend</i> {@code
 * java.util.function.Supplier}, making conversion code necessary only in one direction. At that
 * time, this interface will be officially discouraged.
 *
 * @author Harry Heymann
 * @since 2.0
 */

  /**
   * Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal.
   * That is, each node's subtrees are traversed after the node itself is returned.
   *
   * <p>No guarantees are made about the behavior of the traversal when nodes change while iteration
   * is in progress or when the iterators generated by {@link #children} are advanced.
   *

 * #iterator()} method after the first, and whose iterator is always unmodifiable.
 *
 * <p>The {@code Iterable} specification does not make it absolutely clear what should happen on a
 * second invocation, so implementors have made various choices, including:
 *
 * <ul>
 *   <li>returning the same iterator again
 *   <li>throwing an exception of some kind
 *   <li>or the usual, <i>robust</i> behavior, which all known {@link Collection} implementations

 * type</i> of function is expected, use the method reference {@code function::apply}. A future
 * version of {@code com.google.common.base.Function} will be made to <i>extend</i> {@code
 * java.util.function.Function}, making conversion code necessary only in one direction. At that
 * time, this interface will be officially discouraged.
 *
 * @author Kevin Bourrillion
 * @since 2.0

  }

  @Override
  public EndpointPair<N> incidentNodes(E edge) {
    N nodeU = checkedReferenceNode(edge);
    // requireNonNull is safe because checkedReferenceNode made sure the edge is in the network.
    N nodeV = requireNonNull(nodeConnections.get(nodeU)).adjacentNode(edge);
    return EndpointPair.of(this, nodeU, nodeV);
  }

  @Override
  public Set<N> adjacentNodes(N node) {

 * object). So it is important to not call {@link #dispatch} while holding any locks. This is why
 * {@link #enqueue} and {@link #dispatch} are 2 different methods. It is expected that the decision
 * to run a particular event is made during the state change, but the decision to actually invoke
 * the listeners can be delayed slightly so that locks can be dropped. Also, because {@link
 * #dispatch} is expected to be called concurrently, it is idempotent.
 */