Add a mirrored strategy

bob/learn/tensorflow/configs/MirroredStrategy.py

+import tensorflow as tf
+
+
+def strategy_fn():
+    print("Creating MirroredStrategy strategy.")
+    strategy = tf.distribute.MirroredStrategy()
+    print("MirroredStrategy strategy created.")
+    print("Number of devices: {}".format(strategy.num_replicas_in_sync))
+    return strategy

setup.py

@@ -57,6 +57,7 @@ setup(
         # entry points for bob keras fit --strategy-fn option
         "bob.learn.tensorflow.strategy": [
             "multi-worker-mirrored-strategy = bob.learn.tensorflow.configs.MultiWorkerMirroredStrategy:strategy_fn",
+            "mirrored-strategy = bob.learn.tensorflow.configs.MirroredStrategy:strategy_fn",
         ],
     },
     # Classifiers are important if you plan to distribute this package through