code: public Observable<ServiceResponse<String>> getMetadataWithServiceResponseAsync(String scope) {
          if (scope == null) {
              throw new IllegalArgumentException("Parameter scope is required and cannot be null.");
          }
          if (this.client.apiVersion() == null) {
              throw new IllegalArgumentException("Parameter this.client.apiVersion() is required and cannot be null.");
          }
          return service.getMetadata(scope, this.client.apiVersion(), this.client.acceptLanguage(), this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<String>>>() {
                  @Override
                  public Observable<ServiceResponse<String>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<String> clientResponse = getMetadataDelegate(response);
                          return Observable.just(clientResponse);
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Gets OData metadata XML document.
  
  @param scope A valid scope, i.e. management group, subscription, resource group, or resource ID. Scope used has no effect on metadata returned.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the String object