Course-5, Week-1, Assignment-3, Exercise-1: Jazz improvisation,SymbolicException during

I was working on Jazz Improvisation With LSTM assignment of course-5: Sequence Models. I’m getting the below error(screenshot) during the function. My djmodel & model.compile functions ran successfully. I’m not able to figure out what this error means. Please help. Thank you.

It could mean there is an error in your djmodel() function that the test cases did not catch.