code: def __len__(self):
      return len(self.sentences)
  
file_path: sentence-transformers/examples/unsupervised_learning/MLM/train_mlm.py
imports: from transformers import AutoModelForMaskedLM, AutoTokenizer
  from transformers import DataCollatorForLanguageModeling, DataCollatorForWholeWordMask
  from transformers import Trainer, TrainingArguments
  import sys
  import gzip
  from datetime import datetime
label_desc: Use image node_id 3 for calling the TokenizedSentencesDataset obj's underlying member method code with example usage: obj.__len__() and returns: len