* @param arrays zero or more {@code float} arrays
   * @return a single array containing all the values from the source arrays, in order
   * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit
   *     in an {@code int}
   */
  public static float[] concat(float[]... arrays) {
    long length = 0;
    for (float[] array : arrays) {
      length += array.length;
    }

   * @param arrays zero or more {@code double} arrays
   * @return a single array containing all the values from the source arrays, in order
   * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit
   *     in an {@code int}
   */
  public static double[] concat(double[]... arrays) {
    long length = 0;
    for (double[] array : arrays) {
      length += array.length;
    }

   * @param arrays zero or more {@code float} arrays
   * @return a single array containing all the values from the source arrays, in order
   * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit
   *     in an {@code int}
   */
  public static float[] concat(float[]... arrays) {
    long length = 0;
    for (float[] array : arrays) {
      length += array.length;
    }

  // okay since we have to copy the just-created array anyway.
  public static ImmutableLongArray of(long first, long... rest) {
    checkArgument(
        rest.length <= Integer.MAX_VALUE - 1, "the total number of elements must fit in an int");
    long[] array = new long[rest.length + 1];
    array[0] = first;
    System.arraycopy(rest, 0, array, 1, rest.length);
    return new ImmutableLongArray(array);
  }

  // okay since we have to copy the just-created array anyway.
  public static ImmutableIntArray of(int first, int... rest) {
    checkArgument(
        rest.length <= Integer.MAX_VALUE - 1, "the total number of elements must fit in an int");
    int[] array = new int[rest.length + 1];
    array[0] = first;
    System.arraycopy(rest, 0, array, 1, rest.length);
    return new ImmutableIntArray(array);
  }

*   `tf.keras`:

    *   `Model.fit` major improvements:
        *   You can now use custom training logic with `Model.fit` by overriding
            `Model.train_step`.
        *   Easily write state-of-the-art training loops without worrying about
            all of the features `Model.fit` handles for you (distribution
            strategies, callbacks, data formats, looping logic, etc)

   * @param arrays zero or more {@code double} arrays
   * @return a single array containing all the values from the source arrays, in order
   * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit
   *     in an {@code int}
   */
  public static double[] concat(double[]... arrays) {
    long length = 0;
    for (double[] array : arrays) {
      length += array.length;
    }

    final BloomFilter<Integer> bloomFilter =
        BloomFilter.create(Funnels.integerFunnel(), 15_000_000, 0.01);

    // This check has to be BEFORE the loop because the random insertions can
    // flip GOLDEN_PRESENT_KEY to true even if it wasn't explicitly inserted
    // (false positive).
    assertThat(bloomFilter.mightContain(GOLDEN_PRESENT_KEY)).isFalse();
    for (int i = 0; i < NUM_PUTS; i++) {

     */
    const val CANCEL_AFTER_CLOSE_MILLIS = 60L * 1000

    /**
     * The smallest message that will be compressed. We use 1024 because smaller messages already
     * fit comfortably within a single ethernet packet (1500 bytes) even with framing overhead.
     *
     * For tests this must be big enough to realize real compression on test messages like

   *
   * @param keyOffset 1 if this is the reverse direction of a BiMap, 0 otherwise.
   * @return an {@code Object} that is a {@code byte[]}, {@code short[]}, or {@code int[]}, the
   *     smallest possible to fit {@code tableSize}; or an {@code Object[]} where [0] is one of
   *     these; [1] indicates how many element pairs in {@code alternatingKeysAndValues} are valid;