docstr: Class-specific build method to be overridden by child classes.
code: def _build(self):
      """
      Class-specific build method to be overridden by child classes.
      """
      pass
  
file_path: NeMo/nemo/collections/nlp/data/language_modeling/megatron/bart_dataset.py
imports: import numpy
  from nemo.collections.nlp.data.language_modeling.megatron.dataset_utils import create_masked_lm_predictions, get_samples_mapping
  from nemo.collections.nlp.data.language_modeling.megatron.t5_dataset import T5Dataset
label_desc: Use image node_id 2 for calling the BARTDataset obj's underlying member method code with example usage: obj._build() without return types