code: def testModeStrings(self):
      # check invalid mode strings
      self.open(TESTFN, "wb").close()
      for mode in ("", "aU", "wU+", "U+", "+U", "rU+"):
          try:
              f = self.open(TESTFN, mode)
          except ValueError:
              pass
          else:
              f.close()
              self.fail("%r is an invalid file mode" % mode)
  
imports: import sys
  import os
  import unittest
  from array import array
  from weakref import proxy
  import io
  import _pyio
  from test.support import gc_collect
  from test.support.os_helper import TESTFN
  from test.support import os_helper
  from test.support import warnings_helper
  from collections import UserList
label_desc: Use image node_id 2 for calling the OtherFileTests obj's underlying member method code with example usage: obj.testModeStrings() without return types