docstr: Test streamlit.string_util.decode_ascii.
code: def test_decode_ascii(self):
      """Test streamlit.string_util.decode_ascii."""
      self.assertEqual(
          "test string.", string_util.decode_ascii(b"test string.")
      )
  
file_path: streamlit/lib/tests/streamlit/string_util_test.py
imports: import unittest
  from parameterized import parameterized
  from streamlit import string_util
label_desc: Use image node_id 1 for calling the StringUtilTest obj's underlying member method code with example usage: obj.test_decode_ascii() without return types