Add Group Normalization

tests/ut/python/nn/test_batchnorm.py

@@ -57,6 +57,7 @@ def test_compile():
     input_data = Tensor(np.random.randint(0, 255, [1, 3, 224, 224]).astype(np.float32))
     _executor.compile(net, input_data)
 
+
 class GroupNet(nn.Cell):
     def __init__(self):
         super(GroupNet, self).__init__()
@@ -64,6 +65,7 @@ class GroupNet(nn.Cell):
     def construct(self, x):
         return self.group_bn(x)
 
+
 def test_compile_groupnorm():
     net = nn.GroupNorm(16, 64)
     input_data = Tensor(np.random.rand(1,64,256,256).astype(np.float32))