3x3 convolution with padding.
    Original code has had bias turned off, because Batch Norm would remove the bias either way

def conv3x3(in_channels, out_channels, stride=1):
    """
    3x3 convolution with padding.
    Original code has had bias turned off, because Batch Norm would remove the bias either way
    """
    return nn.Conv2d(in_channels, out_channels, kernel_size=3, stride=stride, padding=1, bias=False)