class_docstr: Builder class for the MMapIndexedDataset class
  
  Args:
      bin_path (str): The path to the data (.bin) file
  
      dtype (Type[numpy.number], optional): The dtype of the index file. Defaults to numpy.int32.
  
      multimodal (bool, optional): Whether the dataset is multimodal. Defaults to False.
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docstr: Add a single item to the dataset
  
  Args:
      tensor (torch.Tensor): The item to add to the data file
  
      mode (int, optional): The mode for the item. Defaults to 0.
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code: def add_item(self, tensor: torch.Tensor, mode: int = 0) -> None:
      """Add a single item to the dataset
  
      Args:
          tensor (torch.Tensor): The item to add to the data file
  
          mode (int, optional): The mode for the item. Defaults to 0.
      """
      np_array = numpy.array(tensor.numpy(), dtype=self.dtype)
      self.data_file.write(np_array.tobytes(order="C"))
      self.sequence_lengths.append(np_array.size)
      if self.multimodal:
          self.sequence_modes.append(mode)
  
imports: import logging
  import os
  import shutil
  import struct
  import time
  from enum import Enum
  from functools import lru_cache
  from itertools import accumulate
  from types import TracebackType
  from typing import List, Optional, Tuple, Type, Union
  import numpy
  import torch
  from megatron.core.datasets.utils import log_single_rank
label_desc: Use image node_id 2 for calling the MMapIndexedDatasetBuilder obj's underlying member method code with example usage: obj.add_item(tensor, mode) without return types