code: public Observable<Page<BackupEngineBaseResourceInner>> listAsync(final String vaultName, final String resourceGroupName) {
          return listWithServiceResponseAsync(vaultName, resourceGroupName)
              .map(new Func1<ServiceResponse<Page<BackupEngineBaseResourceInner>>, Page<BackupEngineBaseResourceInner>>() {
                  @Override
                  public Page<BackupEngineBaseResourceInner> call(ServiceResponse<Page<BackupEngineBaseResourceInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Backup management servers registered to Recovery Services Vault. Returns a pageable list of servers.
  
  @param vaultName The name of the recovery services vault.
  @param resourceGroupName The name of the resource group where the recovery services vault is present.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;BackupEngineBaseResourceInner&gt; object