code: public Observable<DiagnosticCategoryInner> getSiteDiagnosticCategorySlotAsync(String resourceGroupName, String siteName, String diagnosticCategory, String slot) {
          return getSiteDiagnosticCategorySlotWithServiceResponseAsync(resourceGroupName, siteName, diagnosticCategory, slot).map(new Func1<ServiceResponse<DiagnosticCategoryInner>, DiagnosticCategoryInner>() {
              @Override
              public DiagnosticCategoryInner call(ServiceResponse<DiagnosticCategoryInner> response) {
                  return response.body();
              }
          });
      }
docs: Get Diagnostics Category.
  Get Diagnostics Category.
  
  @param resourceGroupName Name of the resource group to which the resource belongs.
  @param siteName Site Name
  @param diagnosticCategory Diagnostic Category
  @param slot Slot Name
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the DiagnosticCategoryInner object