presto-main/src/main/java/io/prestosql/operator/scalar/JsonPathTokenizer.java/JsonPathTokenizer/JsonPathTokenizer
class JsonPathTokenizer:    public JsonPathTokenizer(String path)
    {
        this.path = requireNonNull(path, "path is null");

        if (path.isEmpty()) {
            throw invalidJsonPath();
        }

        // skip the start token
        match('$');
    }