code: public Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>> getWithServiceResponseAsync(final String vaultName, final String resourceGroupName, final String filter, final String skipToken) {
          return getSinglePageAsync(vaultName, resourceGroupName, filter, skipToken)
              .concatMap(new Func1<ServiceResponse<Page<BackupEngineBaseResourceInner>>, Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>> call(ServiceResponse<Page<BackupEngineBaseResourceInner>> page) {
                      String nextPageLink = page.body().nextPageLink();
                      if (nextPageLink == null) {
                          return Observable.just(page);
                      }
                      return Observable.just(page).concatWith(getNextWithServiceResponseAsync(nextPageLink));
                  }
              });
      }
docs: The backup management servers registered to a Recovery Services vault. This returns a pageable list of servers.
  
  @param vaultName The name of the Recovery Services vault.
  @param resourceGroupName The name of the resource group associated with the Recovery Services vault.
  @param filter Use this filter to choose the specific backup management server. backupManagementType { AzureIaasVM, MAB, DPM, AzureBackupServer, AzureSql }.
  @param skipToken The Skip Token filter.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;BackupEngineBaseResourceInner&gt; object