Is it means first layer also re-trained?

I have converted the convolution layer from 3 channels to 4 channels. Is it means the first layer is also re-trained using target images?
model = models.resnet18(pretrained=True)
model.conv1 = nn.Conv2d(4, 64, kernel_size=7, stride=2, padding=3, bias=False)
num_ftrs = model.fc.in_features
model.fc = nn.Linear(num_ftrs, num_classes)

It should be.
The easiest way to verify is just to print the model.conv1.weight and see if it changes when training.