class_docstr: Simple hub download and run test.
code: def test_download_op(self):
      CacheManager().get_operator(
          "image-decode/cv2-rgb", "main", True, True
      )
      CacheManager().get_operator(
          "image-decode/cv2", "main", True, False
      )
  
imports: import unittest
  from towhee.hub.cache_manager import CacheManager
label_desc: Use image node_id 2 for calling the TestCacheManager obj's underlying member method code with example usage: obj.test_download_op() without return types