presto-main/src/main/java/io/prestosql/operator/scalar/MapTransformValueFunction.java/MapTransformValueFunction/MapTransformValueFunction
class MapTransformValueFunction:    private MapTransformValueFunction()
    {
        super(new FunctionMetadata(
                new Signature(
                        "transform_values",
                        ImmutableList.of(typeVariable("K"), typeVariable("V1"), typeVariable("V2")),
                        ImmutableList.of(),
                        mapType(new TypeSignature("K"), new TypeSignature("V2")),
                        ImmutableList.of(
                                mapType(new TypeSignature("K"), new TypeSignature("V1")),
                                functionType(new TypeSignature("K"), new TypeSignature("V1"), new TypeSignature("V2"))),
                        false),
                false,
                ImmutableList.of(
                        new FunctionArgumentDefinition(false),
                        new FunctionArgumentDefinition(false)),
                false,
                false,
                "apply lambda to each entry of the map and transform the value",
                SCALAR));
    }