@Override
        protected Expression newTransform(DataType fieldType) {
            Expression exp = new NGramExpression(null, ngram);
            if (fieldType instanceof CollectionDataType)
                exp = new ForEachExpression(exp);
            return exp;
        }
The implementation of "gram" matching - splitting the incoming text and the queries into
n-grams for matching. This will also validate the gram settings.

@author bratseth
config-model/src/main/java/com/yahoo/schema/processing/NGramMatch.java