code: def test_key_methods(self):
      self.g = gdbm.open(filename, "c")
      self.assertEqual(self.g.keys(), [])
      self.g["a"] = "b"
      self.g["12345678910"] = "019237410982340912840198242"
      self.g[b"bytes"] = b"data"
      key_set = set(self.g.keys())
      self.assertEqual(key_set, set([b"a", b"bytes", b"12345678910"]))
      self.assertIn("a", self.g)
      self.assertIn(b"a", self.g)
      self.assertEqual(self.g[b"bytes"], b"data")
      key = self.g.firstkey()
      while key:
          self.assertIn(key, key_set)
          key_set.remove(key)
          key = self.g.nextkey(key)
      # get() and setdefault() work as in the dict interface
      self.assertEqual(self.g.get(b"a"), b"b")
      self.assertIsNone(self.g.get(b"xxx"))
      self.assertEqual(self.g.get(b"xxx", b"foo"), b"foo")
      with self.assertRaises(KeyError):
          self.g["xxx"]
      self.assertEqual(self.g.setdefault(b"xxx", b"foo"), b"foo")
      self.assertEqual(self.g[b"xxx"], b"foo")
  
imports: from test import support
  from test.support import import_helper, cpython_only
  import unittest
  import os
  from test.support.os_helper import TESTFN, TESTFN_NONASCII, unlink, FakePath
label_desc: Use image node_id 5 for calling the TestGdbm obj's underlying member method code with example usage: obj.test_key_methods() without return types