code: public SimpleModule getExtensionModule() {
  
      if (this.extensionModule == null) {
        this.extensionModule =
            new SimpleModule("oasp.ExtensionModule", new Version(1, 0, 0, null, GROUP_ID, ARTIFACT_ID));
      }
      return this.extensionModule;
    }
docs: Gets access to a generic extension {@link SimpleModule module} for customizations to Jackson JSON mapping.
  
  @see SimpleModule#addSerializer(Class, com.fasterxml.jackson.databind.JsonSerializer)
  @see SimpleModule#addDeserializer(Class, com.fasterxml.jackson.databind.JsonDeserializer)
  
  @return extensionModule