code: def test_modes(self):
      for mode in ["r", "rw", "w", "n"]:
          try:
              self.d = dbm.ndbm.open(self.filename, mode)
              self.d.close()
          except error:
              self.fail()
  
imports: from test.support import import_helper
  from test.support import os_helper
  import os
  import unittest
  import dbm.ndbm
  from dbm.ndbm import error
label_desc: Use image node_id 5 for calling the DbmTestCase obj's underlying member method code with example usage: obj.test_modes() without return types