code: def source_dictionary(self):
      return None
  
imports: import logging
  from argparse import Namespace
  from pathlib import Path
  from typing import List
  from fairseq.data import Dictionary, encoders
  from fairseq.data.audio.audio_utils import get_features_or_waveform
  from fairseq.data.audio.data_cfg import MultitaskConfig
  from fairseq.data.audio.speech_to_text_dataset import S2TDataConfig, SpeechToTextDataset, SpeechToTextDatasetCreator, TextTargetMultitaskData
  from fairseq.tasks import LegacyFairseqTask, register_task
label_desc: Use image node_id 9 for calling the SpeechToTextTask obj's underlying member method code with example usage: obj.source_dictionary() and returns: None