code: def __len__(self) -> int:
      return len(self.dataset)
  
imports: from abc import ABC, abstractmethod
  from dataclasses import dataclass
  from typing import Generator, Optional, Tuple
  import pandas
  from gluonts.dataset import Dataset, DataEntry
  from gluonts.dataset.field_names import FieldName
label_desc: Use image node_id 2 for calling the TrainingDataset obj's underlying member method code with example usage: obj.__len__() and returns: len