return new SingletonImmutableSet<>(element);
  }

  /*
   * TODO: b/315526394 - Skip the Builder entirely for the of(...) methods, since we don't need to
   * worry that we might trigger the fallback to the JDK-backed implementation? (The varargs one
   * _could_, so we could keep it as it is. Or we could convince ourselves that hash flooding is
   * unlikely in practice there, too.)
   */

  /**

	switch event.Event {
	case controllers.EventAdd:
		// pod was added to our cache
		// we get here in 2 cases:
		// 1. new pod was created on our node
		// 2. we were restarted and current existing pods are added to our cache

		// We have no good way to distinguish between these two cases from here. But we don't need to!
		// Existing pods will be handled by the dataplane using `GetAmbientPods`,

     * StackOverflowError: We can't reliably call setException(error).
     *
     * - Any kind of Error from a listener. Even if we could distinguish that case (by exposing some
     * extra state from AbstractFuture), our options are limited: A call to setException() would be
     * a no-op. We could log, but if that's what we really want, we should modify

    // objects indefinitely.
    private void drainQueue() {
      Reference<? extends L> ref;
      while ((ref = queue.poll()) != null) {
        // We only ever register ArrayReferences with the queue so this is always safe.
        ArrayReference<? extends L> arrayRef = (ArrayReference<? extends L>) ref;

     *
     * We need to apply the settings and ack them atomically. This is because some HTTP/2
     * implementations (nghttp2) forbid peers from taking advantage of settings before they have
     * acknowledged! In particular, we shouldn't send frames that assume a new `initialWindowSize`
     * until we send the frame that acknowledges this new size.
     *

    thread.joinSuccessfully(LONG_DELAY_MS);
    assertInterrupted();
  }

  public void testJoinTimeoutMultiInterruptExpired() {
    /*
     * We don't "need" to schedule a thread completion at all here, but by doing
     * so, we come the closest we can to testing that the wait time is
     * appropriately decreased on each progressive join() call.
     */
    TimedThread thread = TimedThread.createWithDelay(LONG_DELAY_MS);

We are going to include this `APIRouter` in the main `FastAPI` app, but first, let's check the dependencies and another `APIRouter`.

## Dependencies

We see that we are going to need some dependencies used in several places of the application.

So we put them in their own `dependencies` module (`app/dependencies.py`).

   * objects per entry.  Instead we use an open-addressed hash table.  This design is basically
   * equivalent to RegularImmutableSet, save that instead of having a hash table containing the
   * elements directly and null for empty positions, we store indices of the keys in the hash table,
   * and ABSENT for empty positions.  We then look up the keys in alternatingKeysAndValues.
   *

  private final ImmutableMap<C, ImmutableMap<R, V>> columnMap;

  @SuppressWarnings("Immutable") // We don't modify this after construction.
  private final int[] rowCounts;

  @SuppressWarnings("Immutable") // We don't modify this after construction.
  private final int[] columnCounts;

  @SuppressWarnings("Immutable") // We don't modify this after construction.
  private final @Nullable V[][] values;

   */
  private static void selectInPlace(int required, double[] array, int from, int to) {
    // If we are looking for the least element in the range, we can just do a linear search for it.
    // (We will hit this whenever we are doing quantile interpolation: our first selection finds
    // the lower value, our second one finds the upper value by looking for the next least element.)