fix lint issues. (#6855)

official/transformer/v2/embedding_layer.py

@@ -36,6 +36,7 @@ class EmbeddingSharedWeights(tf.keras.layers.Layer):
     self.hidden_size = hidden_size
 
   def build(self, input_shape):
+    """Build embedding layer."""
     with tf.name_scope("embedding_and_softmax"):
       # Create and initialize weights. The random normal initializer was chosen
       # arbitrarily, and works well.

official/transformer/v2/metrics.py

@@ -22,7 +22,6 @@ Metrics:
  - ROUGE score. Source:
      https://github.com/tensorflow/tensor2tensor/blob/master/tensor2tensor/utils/rouge.py
 """
-
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function

official/transformer/v2/optimizer.py

@@ -12,8 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
-"""Optimizer from addons and learning rate scheduler.
-"""
+"""Optimizer from addons and learning rate scheduler."""
 
 from __future__ import absolute_import
 from __future__ import division