docs: def evaluate(self, batchsize):
          """Evaluate how well the classifier is doing. Return mean loss and mean accuracy"""
          sum_loss, sum_accuracy = 0, 0
          for i in range(0, self.testsize, batchsize):
              x = Variable(self.x_test[i: i + batchsize])
              y = Variable(self.y_test[i: i + batchsize])
              loss = self.model(x, y)
              sum_loss += loss.data * batchsize
              sum_accuracy += self.model.accuracy.data * batchsize
          return sum_loss / self.testsize, sum_accuracy / self.testsize