code: def test_export_onnx_model(self):
      self.module.export_onnx_model(
          dirname="onnx", input_shape_dict=None, opset_version=10
      )
      self.assertTrue(
          os.path.isfile("onnx/multi_languages_ocr_db_crnn_cls.onnx")
      )
      self.assertTrue(
          os.path.isfile("onnx/multi_languages_ocr_db_crnn_det.onnx")
      )
      self.assertTrue(
          os.path.isfile("onnx/multi_languages_ocr_db_crnn_rec.onnx")
      )
  
file_path: PaddleHub/modules/image/text_recognition/multi_languages_ocr_db_crnn/test.py
imports: import os
  import shutil
  import unittest
  import cv2
  import requests
  import paddlehub
label_desc: Use image node_id 8 for calling the TestHubModule obj's underlying member method code with example usage: obj.test_export_onnx_model() without return types