how I can check the dimension of an HDF file  and is it still an hdf file  if its again passed  another dataset  HDF?
I have an hdf file  which is again divided into trainset and testset  as shown below but when I am trying to check the dimension of hdf it says HDF5 has no attribute “keys”
trainset =          Dataset4DFromHDF5(args.data,
                                 labels=(ref_type,),
                                                          
                                 device=loader_device,

                                 start=args.intervals[0], 
                                 end=args.intervals[1],
                                 crop=args.crop,
                                 augment=args.img_augm,
                                 augment_freq=args.freq_augm)

testset = Dataset4DFromHDF5(args.data,
                                labels=(ref_type,),
                                device=loader_device,
                                start=args.intervals[2], 
                                end=args.intervals[3],
                                crop=args.crop,
                                augment=False,
                                augment_freq=False)

list(trainset.keys())
AttributeError: ‘DatasetDeepPhysHDF5’ object has no attribute ‘keys’