in core/src/main/scala/com/spotify/featran/transformers/NHotWeightedEncoder.scala [67:79]
def addMissingValue(
fb: FeatureBuilder[_],
unseen: MSet[String],
keys: Seq[String],
unseenWeight: Double
): Unit =
if (keys.isEmpty) {
fb.add(name + '_' + MissingValueToken, 1.0)
} else if (unseen.isEmpty) {
fb.skip()
} else {
fb.add(name + '_' + MissingValueToken, unseenWeight)
}