code: def test_dumbdbm_modification(self):
      self.init_db()
      with contextlib.closing(dumbdbm.open(_fname, "w")) as f:
          self._dict[b"g"] = f[b"g"] = b"indented"
          self.read_helper(f)
          # setdefault() works as in the dict interface
          self.assertEqual(f.setdefault(b"xxx", b"foo"), b"foo")
          self.assertEqual(f[b"xxx"], b"foo")
  
imports: import contextlib
  import io
  import operator
  import os
  import stat
  import unittest
  import dbm.dumb
  from test import support
  from test.support import os_helper
  from functools import partial
label_desc: Use image node_id 4 for calling the DumbDBMTestCase obj's underlying member method code with example usage: obj.test_dumbdbm_modification() without return types