code: def __len__(self) -> int:
      raise NotImplementedError
  
file_path: gluonts/src/gluonts/dataset/__init__.py
imports: from dataclasses import dataclass
  from pathlib import Path
  from typing import Any, Dict, Iterator, List, Optional
  from typing_extensions import Protocol, runtime_checkable
  from gluonts.itertools import roundrobin
label_desc: Use image node_id 2 for calling the Dataset obj's underlying member method code with example usage: obj.__len__() without return types