class_docstr: Unit test for serializer.
class_docstr_tok: ["Unit","test","for","serializer","."]
code: def test_empty(self):
      empty_json = to_json(Empty())
      empty_deserialized = from_json(empty_json)
      self.assertTrue(empty_deserialized is Empty())
  
file_path: towhee/tests/unittests/utils/test_serializer.py
imports: import unittest
  import json
  import numpy
  from towhee.runtime.data_queue import Empty
  from towhee.utils.serializer import to_json, from_json
label_desc: Use image node_id 4 for calling the TestSerializer obj's underlying member method code with example usage: obj.test_empty() without return types