code: def __len__(self):
      return sum(self.sizes) // self.batch_size
  
imports: import os
  import types
  import subprocess
  import cloudpickle
  from pyspark.sql import DataFrame
  from torch.utils.data import Dataset, DataLoader
  from zoo.util.utils import get_node_ip
  from zoo.orca.learn.mpi.mpi_runner import MPIRunner
  from zoo.orca.learn.mpi.utils import *
label_desc: Use image node_id 4 for calling the PlasmaNDArrayDataset obj's underlying member method code with example usage: obj.__len__() and returns: unknown