This companion object of class SentimentAnalyzer provides methods for initializing a analyzer instances from training data.

The methods expect the data to be in the following line-based format:

-1 Aggressive self-glorification and a manipulative whitewash.
2 A comedy-drama of nearly epic proportions rooted in a sincere performance by the title character undergoing midlife crisis.
-1 Narratively, Trouble Every Day is a plodding mess.
1 The Importance of Being Earnest, so thick with wit it plays like a reading from Bartlett's Familiar Quotations
0 It's everything you'd expect -- but nothing more.

That is, each line of input should start with a sentiment rating of -2, -1, 0, 1, 2. A negative numbers means that the rest of the line expresses a negative sentiment, as determined by a human rater; positive numbers correspondingly reflect positive sentiments.