small fix: torch.nn.Parameter instead of nn.Linear (#1302)

* nn.Linear module is not defined in Polynomial3 model.
* torch.nn.Parameter is used to defined the members of the model

Co-authored-by: Brian Johnson <brianjo@fb.com>
Co-authored-by: holly1238 <77758406+holly1238@users.noreply.github.com>

Author: 3 people

beginner_source/examples_nn/polynomial_module.py

@@ -49,8 +49,8 @@ def string(self):
 model = Polynomial3()
 
 # Construct our loss function and an Optimizer. The call to model.parameters()
-# in the SGD constructor will contain the learnable parameters of the nn.Linear
-# module which is members of the model.
+# in the SGD constructor will contain the learnable parameters (defined 
+# with torch.nn.Parameter) which are members of the model.
 criterion = torch.nn.MSELoss(reduction='sum')
 optimizer = torch.optim.SGD(model.parameters(), lr=1e-6)
 for t in range(2000):