class_docstr: Do NOT use this directly, use its children.
class_docstr_tok: ["Do","NOT","use","this","directly",",","use","its","children","."]
docstr: Get the filename of the data chunk.
  
  :param chunk_idx:
      which chunk to get
  :return chunk_name:
      return the chunk fname
code: def _get_fname(self, chunk_idx: int) -> str:
      """
      Get the filename of the data chunk.
  
      :param chunk_idx:
          which chunk to get
      :return chunk_name:
          return the chunk fname
      """
      return f"release_data_{str(chunk_idx).zfill(2)}.jsonl"
  
imports: import os
  import json
  from copy import deepcopy
  from parlai.core.message import Message
  from parlai.utils.data import DatatypeHelper
  from parlai.core.teachers import ChunkTeacher
  from .build import build
label_desc: Use image node_id 3 for calling the BaseBB3DataTeacher obj's underlying member method code with example usage: obj._get_fname(chunk_idx) and returns: str, str, str