class_docstr: Memory-mapped text sequence to sequence dataset. Operates pre-tokenized binarized data files.
class_docstr_tok: ["Memory-mapped","text","sequence","to","sequence","dataset",".","Operates","pre-tokenized","binarized","data","files","."]
code: def _check_files_exist(self):
      if not os.path.exists(
          self.src_dataset_prefix + ".bin"
      ) or not os.path.exists(self.src_dataset_prefix + ".idx"):
          raise FileNotFoundError(
              f"{self.src_dataset_prefix}.bin or {self.src_dataset_prefix}.idx not found"
          )
      if not os.path.exists(
          self.tgt_dataset_prefix + ".bin"
      ) or not os.path.exists(self.tgt_dataset_prefix + ".idx"):
          raise FileNotFoundError(
              f"{self.tgt_dataset_prefix}.bin or {self.tgt_dataset_prefix}.idx not found"
          )
  
imports: import os
  import numpy
  import torch
  from nemo.collections.common.tokenizers.tokenizer_spec import TokenizerSpec
  from nemo.collections.nlp.data.language_modeling.megatron.dataset_utils import get_indexed_dataset_, get_samples_mapping
  from nemo.collections.nlp.data.language_modeling.text_memmap_dataset import TextMemMapDataset
  from nemo.core.classes import Dataset
  from nemo.utils import logging
label_desc: Use image node_id 2 for calling the BinarizedMemmapSequenceToSequenceDataset obj's underlying member method code with example usage: obj._check_files_exist() without return types