class_docstr: Simple callback that logs how long each epoch takes, in seconds, to a pytorch lightning log
      
code: def on_train_epoch_end(self, trainer, pl_module):
      curr_time = time.time()
      duration = curr_time - self.epoch_start
      trainer.logger.log_metrics(
          {"epoch_time": duration}, step=trainer.global_step
      )
  
imports: import time
  from pytorch_lightning.callbacks import Callback
  from pytorch_lightning.utilities import rank_zero_only
label_desc: Use image node_id 2 for calling the LogEpochTimeCallback obj's underlying member method code with example usage: obj.on_train_epoch_end(trainer, pl_module) without return types