presto-main/src/main/java/io/prestosql/operator/aggregation/minmaxby/TwoNullableValueStateMapping.java/TwoNullableValueStateMapping/getStateClass
class TwoNullableValueStateMapping:    public static Class<? extends AccumulatorState> getStateClass(Class<?> first, Class<?> second)
    {
        List<Class<?>> key = ImmutableList.of(first, second);
        Class<? extends AccumulatorState> state = STATE_MAPPINGS.get(key);
        checkArgument(state != null, "Unsupported state type combination: (%s, %s)", first.getName(), second.getName());
        return state;
    }