code: public ServiceCall<LanguageModels> listLanguageModels(ListLanguageModelsOptions listLanguageModelsOptions) {
      String[] pathSegments = { "v1/customizations" };
      RequestBuilder builder = RequestBuilder.get(RequestBuilder.constructHttpUrl(getEndPoint(), pathSegments));
      Map<String, String> sdkHeaders = SdkCommon.getSdkHeaders("speech_to_text", "v1", "listLanguageModels");
      for (Entry<String, String> header : sdkHeaders.entrySet()) {
        builder.header(header.getKey(), header.getValue());
      }
      builder.header("Accept", "application/json");
      if (listLanguageModelsOptions != null) {
        if (listLanguageModelsOptions.language() != null) {
          builder.query("language", listLanguageModelsOptions.language());
        }
      }
      return createServiceCall(builder.build(), ResponseConverterUtils.getObject(LanguageModels.class));
    }
docs: List custom language models.
  
  Lists information about all custom language models that are owned by an instance of the service. Use the `language`
  parameter to see all custom language models for the specified language. Omit the parameter to see all custom
  language models for all languages. You must use credentials for the instance of the service that owns a model to
  list information about it.
  
  **See also:** [Listing custom language
  models](https://cloud.ibm.com/docs/services/speech-to-text/language-models.html#listModels-language).
  
  @param listLanguageModelsOptions the {@link ListLanguageModelsOptions} containing the options for the call
  @return a {@link ServiceCall} with a response type of {@link LanguageModels}