code: public Observable<List<ReplicationUsageInner>> listAsync(String resourceGroupName, String vaultName) {
          return listWithServiceResponseAsync(resourceGroupName, vaultName).map(new Func1<ServiceResponse<List<ReplicationUsageInner>>, List<ReplicationUsageInner>>() {
              @Override
              public List<ReplicationUsageInner> call(ServiceResponse<List<ReplicationUsageInner>> response) {
                  return response.body();
              }
          });
      }
docs: Fetches the replication usages of the vault.
  
  @param resourceGroupName The name of the resource group where the recovery services vault is present.
  @param vaultName The name of the recovery services vault.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;ReplicationUsageInner&gt; object