code: def __str__(self):
      return "%s:str" % type(self).__name__
  
imports: from idlelib import run
  import io
  import sys
  from test.support import captured_output, captured_stderr
  import unittest
  from unittest import mock
  import idlelib
  from idlelib.idle_test.mock_idle import Func
label_desc: Use image node_id 1 for calling the S obj's underlying member method code with example usage: obj.__str__() and returns: unknown