class_docstr: Simple operator test
code: def test_add_function(self):
      add_operator = load_local_operator(
          "add_operator", ADD_OPERATOR_PATH
      )
      op = add_operator.AddOperator(1)
      self.assertTrue(isinstance(op, PyOperator))
      self.assertEqual(op(1).sum, 2)
      self.assertEqual(op.shared_type, SharedType.Shareable)
  
      op2 = add_operator.AddOperator(3)
      self.assertEqual(op2(1).sum, 4)
      self.assertEqual(op2.shared_type, SharedType.Shareable)
  
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 3 for calling the TestOperator obj's underlying member method code with example usage: obj.test_add_function() without return types