* {@code x} and {@code y} value pair.
   *
   * @since 20.0
   */
  public static final class LinearTransformationBuilder {

    private final double x1;
    private final double y1;

    private LinearTransformationBuilder(double x1, double y1) {
      this.x1 = x1;
      this.y1 = y1;
    }

    /**
     * Finish building an instance which also maps {@code x = x2} to {@code y = y2}. These values

        dataMap.put("x", "X0");
        Map<String, Object> responseDataMap = new HashMap<>();
        responseDataMap.put("x", "X1");

        indexUpdateCallback.mergeResponseData(dataMap, responseDataMap);

        assertEquals(1, dataMap.size());
        assertEquals("X1", dataMap.get("x"));
    }

    /** Case 3: Only overwrite key (baseKey not set) → generate baseKey, remove overwrite key */

   *     null}.
   */
  @Deprecated
  @J2ktIncompatible
  @GwtIncompatible // propagateIfInstanceOf
  public static <X1 extends Throwable, X2 extends Throwable> void propagateIfPossible(
      @Nullable Throwable throwable, Class<X1> declaredType1, Class<X2> declaredType2)
      throws X1, X2 {
    checkNotNull(declaredType2);
    propagateIfInstanceOf(throwable, declaredType1);
    propagateIfPossible(throwable, declaredType2);

    private InstantiableFactoryMethodChosen(String name) {
      this.name = name;
    }

    public InstantiableFactoryMethodChosen(NotInstantiable x) {
      checkNotNull(x);
      this.name = "x1";
    }

    public static InstantiableFactoryMethodChosen create(NotInstantiable x) {
      return new InstantiableFactoryMethodChosen(x);
    }

    try {
      closingFuture.catching(
          Exception.class,
          new ClosingFunction<Exception, String>() {
            @Override
            public String apply(DeferredCloser closer1, Exception x1) throws Exception {
              return "value3";
            }
          },
          executor);
      fail();
    } catch (IllegalStateException expected3) {
    }
    try {