presto-main/src/main/java/io/prestosql/operator/scalar/MapConstructor.java/MapConstructor/MapConstructor
class MapConstructor:    public MapConstructor()
    {
        super(new FunctionMetadata(
                new Signature(
                        "map",
                        ImmutableList.of(comparableTypeParameter("K"), typeVariable("V")),
                        ImmutableList.of(),
                        TypeSignature.mapType(new TypeSignature("K"), new TypeSignature("V")),
                        ImmutableList.of(arrayType(new TypeSignature("K")), arrayType(new TypeSignature("V"))),
                        false),
                false,
                ImmutableList.of(
                        new FunctionArgumentDefinition(false),
                        new FunctionArgumentDefinition(false)),
                false,
                true,
                DESCRIPTION,
                SCALAR));
    }