docs: public Observable<ManagedBackupShortTermRetentionPolicyInner> beginUpdateAsync(String resourceGroupName, String managedInstanceName, String databaseName, Integer retentionDays) {
          return beginUpdateWithServiceResponseAsync(resourceGroupName, managedInstanceName, databaseName, retentionDays).map(new Func1<ServiceResponse<ManagedBackupShortTermRetentionPolicyInner>, ManagedBackupShortTermRetentionPolicyInner>() {
              @Override
              public ManagedBackupShortTermRetentionPolicyInner call(ServiceResponse<ManagedBackupShortTermRetentionPolicyInner> response) {
                  return response.body();
              }
          });
      }