code: public Observable<List<VaultUsageInner>> listByVaultsAsync(String resourceGroupName, String vaultName) {
          return listByVaultsWithServiceResponseAsync(resourceGroupName, vaultName).map(new Func1<ServiceResponse<List<VaultUsageInner>>, List<VaultUsageInner>>() {
              @Override
              public List<VaultUsageInner> call(ServiceResponse<List<VaultUsageInner>> response) {
                  return response.body();
              }
          });
      }
docs: Fetches the 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;VaultUsageInner&gt; object