code: public Observable<Page<DiagnosticCategoryInner>> listSiteDiagnosticCategoriesAsync(final String resourceGroupName, final String siteName) {
          return listSiteDiagnosticCategoriesWithServiceResponseAsync(resourceGroupName, siteName)
              .map(new Func1<ServiceResponse<Page<DiagnosticCategoryInner>>, Page<DiagnosticCategoryInner>>() {
                  @Override
                  public Page<DiagnosticCategoryInner> call(ServiceResponse<Page<DiagnosticCategoryInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Get Diagnostics Categories.
  Get Diagnostics Categories.
  
  @param resourceGroupName Name of the resource group to which the resource belongs.
  @param siteName Site Name
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;DiagnosticCategoryInner&gt; object