Your script should already thrown an error in from model import vgg, since model doesn’t seem to be a valid module.
I would recommend to look into Python modules 8 to get an idea how your model should be defined inside vgg.py.
That being said, I would recommend to save and load the state_dict approach generally.
Using this approach your files could look like:
# models.py
import torch
import torch.nn as nn

class MyModel(nn.Module):
    def __init__(self):
        super(MyModel, self).__init__()
        self.fc = nn.Linear(1, 1)
        
    def forward(self, x):
        x = self.fc(x)
        return x

# main.py
import torch
import torch.nn as nn

from models import MyModel

model = MyModel
model.load_state_dict(torch.load('STATE_DICT_PATH'))