Pavlovia error: 'slice' undefined?

URL of experiment:

Description of the problem: When I run the above experiment, I get an error that reads:

TypeErrror: A_List is undefined

Can someone help me fix this? I’ve been running into many problems with getting the Iowa Gambling Task 1) correctly piloting on Pavlovia and 2) correctly running on PscyhoPy. I’m sure many of these errors are due to the fact that I am new to this!