presto-main/src/main/java/io/prestosql/operator/scalar/ApplyFunction.java/ApplyFunction/ApplyFunction
class ApplyFunction:    private ApplyFunction()
    {
        super(new FunctionMetadata(
                new Signature(
                        "apply",
                        ImmutableList.of(typeVariable("T"), typeVariable("U")),
                        ImmutableList.of(),
                        new TypeSignature("U"),
                        ImmutableList.of(
                                new TypeSignature("T"),
                                functionType(new TypeSignature("T"), new TypeSignature("U"))),
                        false),
                true,
                ImmutableList.of(
                        new FunctionArgumentDefinition(true),
                        new FunctionArgumentDefinition(false)),
                true,
                true,
                "lambda apply function",
                SCALAR));
    }