Create the Jacobian graph to be ran later in a TF session
  :param predictions: the model's symbolic output (linear output,
      pre-softmax)
  :param x: the input placeholder
  :param nb_classes: the number of classes the model has
  :return:

def jacobian_graph(predictions, x, nb_classes):
  """
  Create the Jacobian graph to be ran later in a TF session
  :param predictions: the model's symbolic output (linear output,
      pre-softmax)
  :param x: the input placeholder
  :param nb_classes: the number of classes the model has
  :return:
  """

  # This function will return a list of TF gradients
  list_derivatives = []

  # Define the TF graph elements to compute our derivatives for each class
  for class_ind in xrange(nb_classes):
    derivatives, = tf.gradients(predictions[:, class_ind], x)
    list_derivatives.append(derivatives)

  return list_derivatives