code: def __len__(self):
      return len(self.test_data)
  
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 1 for calling the InputDataset obj's underlying member method code with example usage: obj.__len__() and returns: len