class_docstr: Test Streamlit utility functions.
class_docstr_tok: ["Test","Streamlit","utility","functions","."]
code: def test_successful_index_(self, input, find_value, expected_index):
      actual_index = util.index_(input, find_value)
      self.assertEqual(actual_index, expected_index)
  
file_path: streamlit/lib/tests/streamlit/util_test.py
imports: import random
  import unittest
  from typing import Dict, List, Set
  from unittest.mock import patch
  import numpy
  from parameterized import parameterized
  from streamlit import util
label_desc: Use image node_id 6 for calling the UtilTest obj's underlying member method code with example usage: obj.test_successful_index_(input, find_value, expected_index) without return types