It looks like you modified the template code for that function. The
return statement no longer returns any values, which is why the variable
parameters (which is assigned with the return value of the function) ends up being “None”. Here’s what that statement looks like in a clean copy of the notebook:
# YOUR CODE ENDS HERE
So why did you change that?
If you want to get a clean copy of the notebook to make sure there is not more damage like this, there is a topic about that on the DLS FAQ Thread.
I did it by mistake