public IEnumerator TestListCategoriesModels()
        {
            Log.Debug("NaturalLanguageUnderstandingServiceV1IntegrationTests", "Attempting to ListSentimentModels...");
            CategoriesModelList listCategoriesModelResponse = null;

            service.ListCategoriesModels(
                callback: (DetailedResponse <CategoriesModelList> response, IBMError error) =>
            {
                Log.Debug("NaturalLanguageUnderstandingServiceV1IntegrationTests", "ListCategoriesModels result: {0}", response.Response);
                listCategoriesModelResponse = response.Result;
                Assert.IsNotNull(listCategoriesModelResponse);
                Assert.IsNotNull(listCategoriesModelResponse.Models);
                Assert.IsNull(error);
            }
                );

            while (listCategoriesModelResponse == null)
            {
                yield return(null);
            }

            foreach (CategoriesModel categoriesModel in listCategoriesModelResponse.Models)
            {
                if (categoriesModel.Name.StartsWith("testString") || categoriesModel.Name.StartsWith("newString"))
                {
                    DeleteModelResults deleteModelResults = null;
                    service.DeleteCategoriesModel(
                        callback: (DetailedResponse <DeleteModelResults> response, IBMError error) =>
                    {
                        Log.Debug("NaturalLanguageUnderstandingServiceV1IntegrationTests", "DeleteCategoriesModel result: {0}", response.Response);
                        deleteModelResults = response.Result;
                        Assert.IsNull(error);
                    },
                        modelId: categoriesModel.ModelId
                        );

                    while (deleteModelResults == null)
                    {
                        yield return(null);
                    }
                }
            }
        }