FastAi What does the slice(lr) do in fit_one_cycle()
In Lesson 3 - planet, I saw these 2 lines of code:

lr = 0.01
learn.fit_one_cycle(5, slice(lr))


if the slice(min_lr, max_lr) then I understand the fit_one_cycle() will use the spread-out Learning Rates from slice(min_lr, max_lr). (Hopefully, my understanding to this is correct)

But in this case slice(lr) only has one parameter, 

What are the differences between fit_one_cycle(5, lr) and fit_one_cycle(5, slice(lr))  ?
And what are the benefits of using slice(lr) instead of lr directly?

Jeremy took a while to explain what slice does in Lesson 5.

What I understood was that the fastai.vision module divides the architecture in 3 groups and trains them with variable learning rates depending on what you input. (Starting layers usually don't require large variations in parameters)

Additionally, if you use 'fit_one_cycle', all the groups will have learning rate annealing with their respective variable learning.

Check Lesson 5 https://course.fast.ai/videos/?lesson=5 (use the transcript finder to quickly go to the 'slice' part)
