code: def test_prints_usage_with_invalid_flag(self):
      output = script_helper.assert_python_failure(
          "-m", "base64", "-x"
      ).err
      self.assertIn(b"usage: ", output)
      self.assertIn(b"-d, -u: decode", output)
  
imports: import unittest
  import base64
  import binascii
  import os
  from array import array
  from test.support import os_helper
  from test.support import script_helper
label_desc: Use image node_id 7 for calling the TestMain obj's underlying member method code with example usage: obj.test_prints_usage_with_invalid_flag() without return types