@Override
  public TransferServices handle(GetTransferServices request) {
    DataVertical transferDataType = request.getTransferDataType();
    // Validate incoming data type parameter
    if (!ActionUtils.isValidTransferDataType(transferDataType)) {
      throw new IllegalArgumentException("Invalid transferDataType: " + transferDataType);
    }

    Set<String> importServices = registry.getImportServices(transferDataType);
    Set<String> exportServices = registry.getExportServices(transferDataType);

    if (importServices.isEmpty() || exportServices.isEmpty()) {
      throw new IllegalArgumentException(
          "[" + transferDataType + "] does not have an import and export service");
    }
    return new TransferServices(transferDataType, exportServices,importServices);
  }
Lists the services available for export and import for a given data type.
portability-api/src/main/java/org/datatransferproject/api/action/transfer/GetTransferServicesAction.java