class_docstr: Simple operator test
code: def test_pyoperator(self):
      self.assertTrue(issubclass(PyOperator, Operator))
  
      py_operator = load_local_operator("py_operator", PY_OPERATOR_PATH)
      op = py_operator.TestPyOperator()
  
      self.assertIsInstance(op, PyOperator)
  
file_path: towhee/tests/unittests/operators/test_operator_base.py
imports: import os
  import unittest
  from pathlib import Path
  from tests.unittests.mock_operators import ADD_OPERATOR_PATH, load_local_operator
  from towhee.operator import SharedType, PyOperator, NNOperator, Operator
label_desc: Use image node_id 2 for calling the TestOperator obj's underlying member method code with example usage: obj.test_pyoperator() without return types