Add license header to NAS (#1788)

src/sdk/pynni/nni/nas/pytorch/enas/trainer.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
 import logging
 import torch
 import torch.optim as optim

src/sdk/pynni/nni/nas/pytorch/fixed.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
 import json
 
 import torch

src/sdk/pynni/nni/nas/pytorch/mutables.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
 import logging
 
 import torch.nn as nn

src/sdk/pynni/nni/nas/pytorch/mutator.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
 import logging
 
 import torch

src/sdk/pynni/nni/nas/pytorch/pdarts/trainer.py

 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
+
 import json
 import logging
 

src/sdk/pynni/nni/nas/pytorch/trainer.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
 import json
 import logging
 from abc import abstractmethod

src/sdk/pynni/nni/nas/pytorch/utils.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
 from collections import OrderedDict
 
 _counter = 0