Determining if a dataset is iterable-style or map-style

Hey there
1.I want to know ,is there any way to understand that our dataset is iterable-style or map-style?

2.Secondly, when we used "torch.utils.data.DataLoader " for a “train_set” is there a way to show us the contents of "torch.utils.data.DataLoader " is iterable or map styled?

3.I think that if we give the ARG ‘sampler’ in "torch.utils.data.DataLoader " ,’=Sampler’ (i.e. sampler=‘Sampler’), we define that our dataset is map-style, and if we set it as ‘Iterable’, we define that our dataset is iterable, AM I RIGHT?

4.I did define a map-style dataset by setting sampler=‘Sampler’ arg in "t=torch.utils.data.DataLoader " . but when I want to call ‘t’ by indexs(i.e. t[i] (like t[0])) it raise the error “‘DataLoader’ object is not subscriptable”. I also used ‘t=torch.utils.data.Sampler’, but it also raised that error too. PLS help me.

I’m so confused by them. I even can’t see the size of my dataloader properly, BCS I don’t like ‘len’ func as it just show the biggest length not the matrix exact size.

PLEASE HELP ME. THANKS A LOT