code: public Observable<List<WorkbookInner>> listByResourceGroupAsync(String resourceGroupName, CategoryType category, List<String> tags, Boolean canFetchContent) {
          return listByResourceGroupWithServiceResponseAsync(resourceGroupName, category, tags, canFetchContent).map(new Func1<ServiceResponse<List<WorkbookInner>>, List<WorkbookInner>>() {
              @Override
              public List<WorkbookInner> call(ServiceResponse<List<WorkbookInner>> response) {
                  return response.body();
              }
          });
      }
docs: Get all Workbooks defined within a specified resource group and category.
  
  @param resourceGroupName The name of the resource group.
  @param category Category of workbook to return. Possible values include: 'workbook', 'TSG', 'performance', 'retention'
  @param tags Tags presents on each workbook returned.
  @param canFetchContent Flag indicating whether or not to return the full content for each applicable workbook. If false, only return summary content for workbooks.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;WorkbookInner&gt; object