Hi @Amol_Singbal ,
It could be some sort of hidden character in that line of code that is causing the problem.
You can try to put a comment sign at the beginning of that line, and retype the same line of code and see if you have any success. Be sure to restart the kernel, clear all output and rerun all the code cells. Making sure your code passed all the tests before submitting your assignment. If that is still not helping, you will need to refresh your workspace and get a fresh copy of the assignment. Here is the instruction for getting a fresh copy of the assignment.