class_docstr: Dataset for training and evaluating left-to-right language models.
  
  Args:
      tokenizer: tokenizer, such as WordTokenizer or CharTokenizer
      dataset: path to data
      max_seq_length: maximum sequence length (in tokens) of input tensors
      batch_step: distance (in tokens) between two successive sequences of
          the text. By default, it is equal to max_seq_length which corresponds
          to splitting text into disjoint segments covering full dataset
      use_cache: bool value, defaults to False. Determines whether the preprocessed,
          tokenized dataset should be cached into a pickle file. If true, cache is saved
          at the path provided in `dataset`.
class_docstr_tok: ["Dataset","for","training","and","evaluating","left-to-right","language","models",".","Args",":","tokenizer",":","tokenizer",",","such","as","WordTokenizer","or","CharTokenizer","dataset",":","path","to","data","max_seq_length",":","maximum","sequence","length","(","in","tokens",")","of","input","tensors","batch_step",":","distance","(","in","tokens",")","between","two","successive","sequences","of","the","text",".","By","default",",","it","is","equal","to","max_seq_length","which","corresponds","to","splitting","text","into","disjoint","segments","covering","full","dataset","use_cache",":","bool","value",",","defaults","to","False",".","Determines","whether","the","preprocessed",",","tokenized","dataset","should","be","cached","into","a","pickle","file",".","If","true",",","cache","is","saved","at","the","path","provided","in","`","dataset","`","."]
code: def __len__(self):
      return (len(self.ids) - self.max_seq_length) // self.batch_step
  
imports: import io
  import json
  from typing import Optional
  import braceexpand
  import numpy
  import webdataset
  from torch.utils.data import Dataset, IterableDataset
  from nemo.collections.common.tokenizers.tokenizer_spec import TokenizerSpec
  from nemo.collections.nlp.data.data_utils import dataset_to_ids
  from nemo.utils import logging
label_desc: Use image node_id 2 for calling the L2RLanguageModelingDataset obj's underlying member method code with example usage: obj.__len__() and returns: unknown