docstr: Gets called at the beginning of each fit_batch.
docstr_tok: ["Gets","called","at","the","beginning","of","each","fit_batch","."]
code: def on_fit_batch_start(self, batch, should_step):
      """Gets called at the beginning of each fit_batch."""
      # check if we need to switch optimizer
      # if so change the optimizer from Adam to SGD
      self.check_and_reset_optimizer()
  
file_path: speechbrain/recipes/CommonVoice/ASR/transformer/train.py
imports: import sys
  import torch
  import torchaudio
  import logging
  import speechbrain
  from hyperpyyaml import load_hyperpyyaml
  from speechbrain.tokenizers.SentencePiece import SentencePiece
  from speechbrain.utils.distributed import run_on_main, if_main_process
  from speechbrain.utils.data_utils import undo_padding
label_desc: Use image node_id 3 for calling the ASR obj's underlying member method code with example usage: obj.on_fit_batch_start(batch, should_step) without return types