Add keras layer and model tests.

3 jobs for dev_tf2 in 34 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Lint
passed #302963
docker
lint

00:00:18

 
  Test
failed #302964
docker
unittests_py2

00:00:14

failed #302965
docker
unittests_py3

00:00:16

 
Name Stage Failure
failed
unittests_py3 Test There is an unknown failure, please try again
  File "/builds/3pia/lbn/test.py", line 340, in test_keras_layer
self.assertAlmostEqual(output[0, 0], 0.321891, 5)
AssertionError: 0.5486644 != 0.321891 within 5 places

----------------------------------------------------------------------
Ran 19 tests in 0.386s

FAILED (failures=1)
ERROR: Job failed: exit code 1
failed
unittests_py2 Test There is an unknown failure, please try again
  File "test.py", line 340, in test_keras_layer
self.assertAlmostEqual(output[0, 0], 0.321891, 5)
AssertionError: 0.79599524 != 0.321891 within 5 places

----------------------------------------------------------------------
Ran 19 tests in 0.351s

FAILED (failures=1)
ERROR: Job failed: exit code 1