@SuppressWarnings("unused") // Required for automatic type inference
  public static <K> Builder0<K> forClass(final Class<K> type) {
    return new Builder0<>();
  }
@Test(expected = IllegalArgumentException.class)
  public void shouldThrowIfHandlerSupplierReturnsNullHandlerR2() {
    HandlerMaps.forClass(BaseType.class)
        .withArgTypes(String.class, Integer.class)
        .withReturnType(Number.class)
        .put(LeafTypeA.class, () -> null)
        .build();
  }