class_docstr: Random Dataset.
  
  This class is modified from RandomDataset in
  https://github.com/PyTorchLightning/pytorch-lightning/
  blob/master/pytorch_lightning/demos/boring_classes.py
  
  :param _type_ Dataset: _description_
code: def __len__(self) -> int:
      return self.len
  
file_path: BigDL/python/nano/example/pytorch/inference_optimizer/export_model/export_model.py
imports: import torch
  from torchvision.models import resnet50
  from bigdl.nano.pytorch import InferenceOptimizer
  from torch.utils.data import DataLoader, Dataset
label_desc: Use image node_id 3 for calling the RandomDataset obj's underlying member method code with example usage: obj.__len__() and returns: self