docstr: Gets called at the beginning of each epoch
docstr_tok: ["Gets","called","at","the","beginning","of","each","epoch"]
code: def on_stage_start(self, stage, epoch):
      """Gets called at the beginning of each epoch"""
  
      # Re-initialize metrics.
      if stage != sb.Stage.TRAIN:
          self.cer_metric = self.hparams.cer_computer()
          self.ctc_metric = self.hparams.ctc_computer()
          self.coer_metric = self.hparams.coer_computer()
          self.cver_metric = self.hparams.cver_computer()
  
file_path: speechbrain/recipes/MEDIA/SLU/CTC/train_hf_wav2vec.py
imports: import sys
  import torch
  import logging
  import speechbrain
  from hyperpyyaml import load_hyperpyyaml
  from speechbrain.dataio.batch import PaddedBatch
  from speechbrain.utils.distributed import run_on_main
  from media_prepare import prepare_media
label_desc: Use image node_id 4 for calling the SLU obj's underlying member method code with example usage: obj.on_stage_start(stage, epoch) without return types