C1W1 Programming Assignment: Your First GAN submission error

That error sounds like there is something structurally wrong or corrupted about your notebook. Are you sure that you didn’t work on it with any tools other than the course website?

Regardless of how the error was generated, my suggestion of the best thing to try would be to get a clean copy of the notebook using the first topic on the DLS FAQ Thread. Then very carefully “copy/paste” over just your solution code from the “YOUR CODE HERE” sections and then try to submit again (after checking that all the local tests still pass, of course).

Please try that and then let us know if that helped or not.