An abstract class for all transforms

[chsasank]

Shouldn't there be a base class for all transforms like torch.utils.data.Dataset?

It can be:

class Transform(object):
    def __init__():
        pass

    def __call__():
        raise NotImplementedError

This makes transforms transparent and easy to refer in other functions like Compose.

[alykhantejani]

Transforms don't necessarily have to be classes, they can be any callable (i.e. functions + classes)

[fmassa]

Given the discussions in #230, I'm not sure there is a need to an abstract class. I'm closing this issue, but let me know if you think otherwise and we can re-open it.