There are many problems here.
1) Are you running in [Test], [Train], or [Trade] mode? Did you account for how the code operates in each mode? Should you be using run() or main() in this case, and why?
2) Unless "6A_M", "6B_M", and "6C_M" are actually assets in your asset list with existing T6 historical data, this code is wrong. Lose the asset() call and consider using of() instead of loop(). of() can be used to set a string.
3) I see you are loading a CSV file, but I do not see your code actually doing anything with the loaded file. You're not even parsing it into a dataset, so I'm not sure what you expected here.