dev_set is not defined

[Dirkster99]

Hi, thanks for your extremelly cool posts :-) especially about PySpark since articles on that are rather sparse. I am just confused about the 'dev_set' being used in your code at [In 71] about the first N-Gram evaluation:

https://github.com/tthustla/setiment_analysis_pyspark/blob/master/Sentiment%20Analysis%20with%20PySpark.ipynb

I cannot see any definition for the dev_set and receive thus an error and was wondering if this is a typo and you meant to put val_set instead?