presto-main/src/main/java/io/prestosql/operator/scalar/JsonStringToMapCast.java/JsonStringToMapCast/specialize
class JsonStringToMapCast:    @Override
    public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, Metadata metadata)
    {
        return JSON_TO_MAP.specialize(boundVariables, arity, metadata);
    }