All tests passed but getting 50% because 'gen' is not defined

[ai_curious]

The answer is very likely to be the exact same as the one in this thread, which describes the exact same error:

There was a problem grading your submission. Details: name 'gen' is not defined

Week 4: Handling Complex Images - Happy or Sad Dataset Model reached at accuracy working very well but after submitting its give error like: There was a problem grading your submission. Details: name ‘gen’ is not defined