To be honest I dont think I am using this the right way. Are you suggesting that I do the following:
img_transform = Compose([Normalize(mean, std),
                                 RandomFlip(random_state),
                                 RandomRotate90(num_rotate),
                                 ToTensor(expand_dims=True, dtype=self.label_dtype)
                                 ])

Then at what stage would I pass the actual image or sample on which the transformations are to be applied?

Also, normalization should come after the  ToTensor  transformation.

Noted. Can you please explain why it makes a difference to normalize after ToTensor.
Thanks