[OPS] Minor edits.

Author: eaplatanios

api/src/main/scala/org/platanios/tensorflow/api/ops/io/data/Dataset.scala

@@ -235,7 +235,9 @@ object Dataset {
     val GroupByWindowDataset: data.GroupByWindowDataset.type = data.GroupByWindowDataset
 
     def fromGenerator[T, O, DA, D, S](
-        generator: () => Iterable[T], outputDataType: DA, outputShape: S = null
+        generator: () => Iterable[T],
+        outputDataType: DA,
+        outputShape: S = null
     )(implicit
         evDAToD: DataTypeAuxToDataType.Aux[DA, D],
         evData: Data.Aux[T, O, D, S],
@@ -285,7 +287,9 @@ object Dataset {
     * @return Constructed dataset.
     */
   private[api] def fromGenerator[T, O, DA, D, S](
-      generator: () => Iterable[T], outputDataType: DA, outputShape: S = null
+      generator: () => Iterable[T],
+      outputDataType: DA,
+      outputShape: S = null
   )(implicit
       evDAToD: DataTypeAuxToDataType.Aux[DA, D],
       evData: Data.Aux[T, O, D, S],

tpu/src/main/scala/org/platanios/tensorflow/tpu/Ops.scala

@@ -158,5 +158,11 @@ private[tpu] object Ops {
     tf.gradientsRegistry.registerNonDifferentiable("InfeedEnqueueTuple")
     tf.gradientsRegistry.registerNonDifferentiable("InfeedDequeue")
     tf.gradientsRegistry.registerNonDifferentiable("InfeedDequeueTuple")
+
+    tf.gradientsRegistry.register("CrossReplicaSum", crossReplicaSumGradient)
+
+    private[this] def crossReplicaSumGradient(op: Op, outputGradients: Seq[OutputLike]): Seq[OutputLike] = {
+      Seq(crossReplicaSum(outputGradients.head))
+    }
   }
 }

tpu/src/main/scala/org/platanios/tensorflow/tpu/Topology.scala

@@ -1,5 +1,23 @@
-package org.platanios.tensorflow.tpu
-
-class Topology {
-
-}
+///* Copyright 2017-18, Emmanouil Antonios Platanios. All Rights Reserved.
+// *
+// * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// * use this file except in compliance with the License. You may obtain a copy of
+// * the License at
+// *
+// *     http://www.apache.org/licenses/LICENSE-2.0
+// *
+// * Unless required by applicable law or agreed to in writing, software
+// * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// * License for the specific language governing permissions and limitations under
+// * the License.
+// */
+//
+//package org.platanios.tensorflow.tpu
+//
+///**
+//  * @author Emmanouil Antonios Platanios
+//  */
+//case class Topology(meshShape: (Int, Int, Int), deviceCoordinates) {
+//
+//}