The definition of CifarVggnet is still missing.
You should have some code like:
class CifarVggnet(nn.Module):
    def __init__(self):
        super(CifarVggnet, self).__init__()
        self....

    def forward(self, x):
        ...

Either define it in the same file before creating an instance of this model or import it from another file, where it was defined.