product_id_map is never updated in preprocess_mtl.py

[mukurgupta]

Thanks for the dataset and well structured code.

In preprocess_mtl.py, product_id_map is never updated. Hence the product_id in the processed csv is always zero. On a small 1 week sample, my experiments with updating product_id show much higher AUC than the reported numbers in the paper. Is this a bug?

Thank you.