presto-main/src/main/java/io/prestosql/sql/planner/plan/SampleNode.java/SampleNode/fromType
class SampleNode:        public static Type fromType(SampledRelation.Type sampleType)
        {
            switch (sampleType) {
                case BERNOULLI:
                    return Type.BERNOULLI;
                case SYSTEM:
                    return Type.SYSTEM;
                default:
                    throw new UnsupportedOperationException("Unsupported sample type: " + sampleType);
            }
        }