docs: public GetDocumentDownloadResponse getDocumentDownload(String documentId) {
          checkNotNull(documentId, "documentId should not be null.");
          GetDocumentDownloadRequest request = new GetDocumentDownloadRequest();
          request.setDocumentId(documentId);
          InternalRequest internalRequest = this.createRequest(HttpMethodName.GET, request, DOC, request.getDocumentId());
          internalRequest.addParameter("download", null);
          GetDocumentDownloadResponse response;
          try {
              response = this.invokeHttpClient(internalRequest, GetDocumentDownloadResponse.class);
          } finally {
              try {
                  internalRequest.getContent().close();
              } catch (Exception e) {
                  // ignore exception
              }
          }
  
          return response;
      }