class_docstr: Unit test for serializer.
class_docstr_tok: ["Unit","test","for","serializer","."]
code: def test_np_fail(self):
      with self.assertRaises(TypeError):
          arr = np.arange(4)
          json.dumps(arr)
  
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 1 for calling the TestSerializer obj's underlying member method code with example usage: obj.test_np_fail() without return types