code: public JsonMappingOption yourUltimateCustomizer(Consumer<Object> yourUltimateCustomizer) {
          if (yourUltimateCustomizer == null) {
              throw new IllegalArgumentException("The argument 'yourUltimateCustomizer' should not be null.");
          }
          this.yourUltimateCustomizer = OptionalThing.of(yourUltimateCustomizer);
          return this;
      }
docs: Set up the your rule for JSON. <br>
  The provided object in lambda is JSON engine customizer e.g. GsonBuilder. <br>
  Use 'downcast' or 'instanceof' in your callback.
  @param yourUltimateCustomizer The callback for customizing JSON engine as your rule. (NotNull)
  @return this. (NotNull)