update import statements

Author: bharathgs

nalu/core/nac_cell.py

@@ -1,7 +1,8 @@
 from torch import Tensor, nn
 from torch.nn.parameter import Parameter
 from torch.nn.init import xavier_uniform_
-from torch.nn.functional import tanh, sigmoid, linear
+from torch.nn.functional import linear
+from torch import sigmoid, tanh
 
 
 class NacCell(nn.Module):

nalu/core/nalu_cell.py

@@ -1,7 +1,8 @@
 from torch import Tensor, exp, log, nn
 from torch.nn.parameter import Parameter
 from torch.nn.init import xavier_uniform_
-from torch.nn.functional import sigmoid, linear
+from torch.nn.functional import linear
+from torch import sigmoid
 from .nac_cell import NacCell