'TimeNet' object has no attribute 'ar_weights' in model.fit() when n_lags is not set but ar_reg is set

[akosmaroy]

Prerequisites

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Describe the bug

I'm getting the following exception when calling model.fit():

'TimeNet' object has no attribute 'ar_weights'

To Reproduce

Create a NeuralProphet object with the following parameters:

        prophet_parameters = {
            # 'n_lags': 79,   <- this parameter is not set
            'ar_reg': 0.08971683614862916,   # <- this parameter is set
            'ar_layers': [116, 116, 116, 116, 116, 116],  # <- AR related parameter, but doesn't have an impact on the exception
            # the rest probably is not relevant to this bug
            'daily_seasonality': False,
            'weekly_seasonality': 'auto',
            'yearly_seasonality': 'auto',
            'accelerator': 'auto',
            'collect_metrics': ["MSE", "MAE", "RMSE"],
            'quantiles': quantiles,
            'n_forecasts': 2,
            'lagged_reg_layers': [82, 82], 
            'trend_reg': 0.9706135322078026,
            'n_changepoints': 91,
            'seasonality_mode': 'multiplicative',
            'seasonality_reg': 0.7543763277837088,
            'future_regressors_model': 'linear',
            'learning_rate': 1e-3,
        }

And call model.fit(). The exception is not thrown immediately, in this case it's thrown at epoch 67. Setting the 'n_lags': parameter makes it not throw the exception, as does removing both 'n_lags' and 'ar_reg'

The fact that the exception is thrown so late, e.g. on epoch 67 - implies that the model internal structure changes between epochs?

Expected behavior

model.fit() should not through this exception.

What actually happens

An exception with the following message is thrown:

'TimeNet' object has no attribute 'ar_weights'

Screenshots

n/a

Environment (please complete the following information):

Python 3.10.12
Ubuntu 22.04 in WSL on Windows 11
NeuralProphet installed from github latest, 2354356

Additional context

n/a