public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName, boolean maintainType) {
        return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, maintainType);
    }
@Test
    public void testNullBaseType() {
        assertThatThrownBy(() -> RuntimeTypeAdapterFactory.of(null))
            .isInstanceOf(NullPointerException.class);
    }