Incorrect Membership Inference Attack

[rufimelo99]

Describe the bug
PR #2 introduced a conceptual bug.
Incorrect Membership Inference Attack example on MNIST dataset.
The attack did not use all the class probabilities. This problem is a multi-class one.

To Reproduce

•  - Just running the example python examples/mnist/membership_inference_attack.py

Expected behaviour
The behaviour should be similar. The attacker model should not receive 1 feature, but 10 instead.