MisconfigurationException: `train_dataloader` must be implemented to be used with the Lightning Trainer

[famube]

Hi,
I tried to run jerex_train.py in a Kaggle environment using the default configurations (except distribution.gpus=[0] distribution.prepare_data_per_node=true, the latter due to a conflict error with DataModule configuration), and got the following error:

Error executing job with overrides: ['distribution.gpus=[0]', 'distribution.prepare_data_per_node=true']
Traceback (most recent call last):
  File "jerex_train.py", line 20, in train
    model.train(cfg)
  File "/kaggle/working/jerex/model.py", line 341, in train
    trainer.fit(model, datamodule=data_module)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py", line 769, in fit
    self._fit_impl, model, train_dataloaders, val_dataloaders, datamodule, ckpt_path
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py", line 721, in _call_and_handle_interrupt
    return trainer_fn(*args, **kwargs)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py", line 809, in _fit_impl
    results = self._run(model, ckpt_path=self.ckpt_path)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py", line 1215, in _run
    self.strategy.setup(self)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/strategies/single_device.py", line 72, in setup
    super().setup(trainer)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/strategies/strategy.py", line 139, in setup
    self.setup_optimizers(trainer)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/strategies/strategy.py", line 129, in setup_optimizers
    self.lightning_module
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/core/optimizer.py", line 180, in _init_optimizers_and_lr_schedulers
    optim_conf = model.trainer._call_lightning_module_hook("configure_optimizers", pl_module=model)
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py", line 1593, in _call_lightning_module_hook
    output = fn(*args, **kwargs)
  File "/kaggle/working/jerex/model.py", line 194, in configure_optimizers
    dataloader = self.train_dataloader()
  File "/opt/conda/lib/python3.7/site-packages/pytorch_lightning/core/hooks.py", line 494, in train_dataloader
    raise MisconfigurationException("`train_dataloader` must be implemented to be used with the Lightning Trainer")
pytorch_lightning.utilities.exceptions.MisconfigurationException: `train_dataloader` must be implemented to be used with the Lightning Trainer

Set the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace.