code: def __len__(self):
      return len(self.features)
  
file_path: NeMo/nemo/collections/nlp/data/dialogue/dataset/dialogue_gpt_generation_dataset.py
imports: import copy
  import torch
  from nemo.collections.nlp.data.dialogue.dataset.dialogue_dataset import DialogueDataset
label_desc: Use image node_id 3 for calling the DialogueGPTGenerationDataset obj's underlying member method code with example usage: obj.__len__() and returns: len