Fix ut 1.15up3 (#846)

* fix mixed precision not support tf1.15UP3

Author: VincyZhang

examples/helloworld/tf_example3/requirements.txt

@@ -1,2 +1,2 @@
-intel-tensorflow==1.15.2
+https://storage.googleapis.com/intel-optimized-tensorflow/intel_tensorflow-1.15.0up3-cp37-cp37m-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
 tf_slim

test/test_bf16_convert.py

@@ -290,6 +290,7 @@ def test_do_transform(self):
         self.assertEqual(new_relu2.attr["T"].type, dtypes.bfloat16)
         self.assertTrue("relu2_BF16toFP32" in new_conv3.input)
 
+
     @unittest.skipIf(tf.version.VERSION > '2.5.0', " Skip test_bf16_fallback case for tf 2.6.0 and above.")
     def test_bf16_fallback(self):
         os.environ['FORCE_BF16'] = '1'