Data augmentation proposal

[rickwierenga]

It would be great if DataLoaders could facilitate data augmentation on batches. I would like to make a proposal for a possible implementation of this.

Start by defining what an augmentation is:

typealias Augmentation = (SomeBatch) -> SomeBatch

Then create a modifier as proposed in #14:

func augmenting(_ augmentation: @escaping Augmentation) -> Self {
    var mutableSelf = self.copy()
    mutableSelf.augmentation = augmentation
    return mutableSelf
}

Make this a requirement on all S5TFDataLoaders:

var augmentation: Augmentation? { get }

Apply the augmentation when loading data (in getElement(at:)):

listOfData.map(augmentation)

Result:

MNIST.train.augmenting(flipRight).augmenting(blur(0.2)).batched(32)

We should offer a list of predefined augmentations using SwiftCV.

Simplified example: https://colab.research.google.com/drive/1YCyx59FXcDXDrtGBHcRFKmbakSNScAJk.