code: public Observable<Void> purgeDeletedAsync(String vaultName, String location) {
          return purgeDeletedWithServiceResponseAsync(vaultName, location).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Permanently deletes the specified vault. aka Purges the deleted Azure key vault.
  
  @param vaultName The name of the soft-deleted vault.
  @param location The location of the soft-deleted vault.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request