Model_heplers.py in is_overridden > raise ValueError("Expected a parent")

I am running on a new remote server a code that used to work on another remote server. I think I setup things in the same way, but when I run my training script, I get this error:

Traceback (most recent call last):
File “train_model.py”, line 146, in
seq_len=seq_len, mname=mname)
File “/home/ds/AI-projects/hss_bearing_mk2/hss_bearing_mk2/models/pytorch_models.py”, line 322, in train_test
trainer.fit(model, datamodule=dm)
File “/home/ds/anaconda3/envs/hss_bearings/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py”, line 552, in fit
self._run(model)
File “/home/ds/anaconda3/envs/hss_bearings/lib/python3.7/site-packages/pytorch_lightning/trainer/trainer.py”, line 849, in _run
self.config_validator.verify_loop_configurations(model)
File “/home/ds/anaconda3/envs/hss_bearings/lib/python3.7/site-packages/pytorch_lightning/trainer/configuration_validator.py”, line 34, in verify_loop_configurations
self.__verify_train_loop_configuration(model)
File “/home/ds/anaconda3/envs/hss_bearings/lib/python3.7/site-packages/pytorch_lightning/trainer/configuration_validator.py”, line 49, in __verify_train_loop_configuration
has_training_step = is_overridden(“training_step”, model)
File “/home/ds/anaconda3/envs/hss_bearings/lib/python3.7/site-packages/pytorch_lightning/utilities/model_helpers.py”, line 45, in is_overridden
> raise ValueError(“Expected a parent”)

Here is the part of code that looks buggy for some reason:

    model = get_model(mname=mname)

    dm = DataModule(
        X_train=X_train,
        y_train=y_train,
        X_val=X_val,
        y_val=y_val,
        X_test=X_test,
        y_test=y_test,
        keys_train=keys_train,
        keys_val=keys_val,
        keys_test=keys_test,
        seq_len=seq_len,
        batch_size=batch_size,
        num_workers=4
    )
    # trainer.logger_connector.callback_metrics
    trainer.fit(model, datamodule=dm)

Is it something related to environment setup? Something overridden by something something??

EDIT: I tried to run my project locally in a newly created environment and I have the same error.

EDIT 2: My DataModule inherits from LightningDataModule

class DataModule(pl.LightningDataModule):

The problem was that model was inheriting from nn.Module instead of from pl.LightningModule