code: def test_loss_gradient(self):
      grad = self.art_model.loss_gradient(
          self.x_test_diabetes[:4], self.y_test_diabetes[:4]
      )
      np.testing.assert_equal(len(np.unique(grad[0])), 10)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import unittest
  import numpy
  from art.estimators.regression.keras import KerasRegressor
  from tests.utils import TestBase, master_seed, get_tabular_regressor_kr
label_desc: Use image node_id 9 for calling the TestKerasRegressorFunctional obj's underlying member method code with example usage: obj.test_loss_gradient() without return types