Fit Error: validation_step() takes 3 positional arguments but 4 were given
Common bugs:
Hello, I installed pytorch lightning like
pip install git+https://github.com/williamFalcon/pytorch-lightning.git@master --upgrade
(btw, i couldnt install by pip install pytorch_lightning: i got error related to setuptools even i have setuptools)
then run following scripts which described in 'How do I use it'
I got an error at section 2 (Fit with a trainer)
Describe the bug
trainer.fit(model)


validation_step() takes 3 positional arguments but 4 were given


Environment:

OS: Ubuntu 18.04
Python: 3.6.8
Anaconda: 1.7.2
torch: 1.2.0
torchvision: 0.4.0
pytorch_lightning: 0.4.4

I'm sorry that I'm not fluent English speaker and hope we'll get figure it out.