Documentation improvements

[Daniel (深度碎片)]

@Daniel

So, I go to check on the docs, the second sentence makes perfect sense to explain the missing puzzle I encountered above:

Create a ItemList in path from filenames in items . create_func will default to open_image .

However, I could not locate the place where items.create_func is set to open_image , in fact the items.create_func seem not exist

First of all, I found the exact codes for turning Path object into Image object below

Second, there is no such thing called items.create_func. So, I would like to rewrite the sentence as follows

It inherits from ItemList and overwrite ItemList.get to call open_image in order to turn an image file in Path object into an Image object.

What do you think? Thanks
@stas @sgugger