unit1/01 clarity needed

[ppbrown]

I'm trying to wade my way through
https://github.com/huggingface/diffusion-models-class/blob/main/unit1/01_introduction_to_diffusers.ipynb

Fairly informative overall, but a few things mire me down, in Step 4:

1. It is confusing that the IMAGE shows 5 green blocks, and the description says "down_block_types correspond to the [green blocks]"... but in the code, down_block_types has 4 entries. Super confusing. Image needs to be remade to match up with code better.

2. It is completely unclear what "block_out_channels" is for.

3. "Middle block" is shown very noticably in the image, but there is zero explaination for them that I can see? They arent even refernced visibly in the code.