then you can fill in the weights and bias of the fc2 layer and disable gradients for them:
my_resnet.fc2 = torch.nn.Linear(10, 1)
my_resnet.fc2.weight.requires_grad = False
my_resnet.fc2.bias.requires_grad = False
my_resnet.fc2.weight.copy_(your_custom_weights)
my_resnet.fc2.bias.copy_(your_custom_bias)
# If you don't have bias you can do my_resnet.fc2.bias.fill_(0)