code: public ServiceFuture<List<BackupEngineBaseResourceInner>> getAsync(final String vaultName, final String resourceGroupName, final String filter, final String skipToken, final ListOperationCallback<BackupEngineBaseResourceInner> serviceCallback) {
          return AzureServiceFuture.fromPageResponse(
              getSinglePageAsync(vaultName, resourceGroupName, filter, skipToken),
              new Func1<String, Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<BackupEngineBaseResourceInner>>> call(String nextPageLink) {
                      return getNextSinglePageAsync(nextPageLink);
                  }
              },
              serviceCallback);
      }
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.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object