presto-main/src/main/java/io/prestosql/operator/scalar/JsonFunctions.java/JsonFunctions/varcharIsJsonScalar
class JsonFunctions:    @ScalarFunction("is_json_scalar")
    @LiteralParameters("x")
    @SqlType(StandardTypes.BOOLEAN)
    public static boolean varcharIsJsonScalar(@SqlType("varchar(x)") Slice json)
    {
        return isJsonScalar(json);
    }