class_docstr: Class for speaker embedding training
docstr: Gets called at the beginning of an epoch.
docstr_tok: ["Gets","called","at","the","beginning","of","an","epoch","."]
code: def on_stage_start(self, stage, epoch=None):
      """Gets called at the beginning of an epoch."""
      if stage != sb.Stage.TRAIN:
          self.error_metrics = self.hparams.error_stats()
  
file_path: speechbrain/recipes/VoxCeleb/SpeakerRec/train_speaker_embeddings.py
imports: import os
  import sys
  import random
  import torch
  import torchaudio
  import speechbrain
  from speechbrain.utils.data_utils import download_file
  from hyperpyyaml import load_hyperpyyaml
  from speechbrain.utils.distributed import run_on_main
label_desc: Use image node_id 3 for calling the SpeakerBrain obj's underlying member method code with example usage: obj.on_stage_start(stage, epoch) without return types