Question about Skip connection block in ResNet

[m7mdhka]

Hello, what is the strd and multiplier do here? what are the use for?

class BasicBlock(nn.Module):
    multiplier=1
    def __init__(self, input_num_planes, num_planes, strd=1):
        super(BasicBlock, self).__init__()
        self.conv_layer1 = nn.Conv2d(in_channels=input_num_planes, out_channels=num_planes, kernel_size=3, stride=stride, padding=1, bias=False)
        self.batch_norm1 = nn.BatchNorm2d(num_planes)
        self.conv_layer2 = nn.Conv2d(in_channels=num_planes, out_channels=num_planes, kernel_size=3, stride=1, padding=1, bias=False)
        self.batch_norm2 = nn.BatchNorm2d(num_planes)
 
        self.res_connnection = nn.Sequential()
        if strd > 1 or input_num_planes != self.multiplier*num_planes:
            self.res_connnection = nn.Sequential(
                nn.Conv2d(in_channels=input_num_planes, out_channels=self.multiplier*num_planes, kernel_size=1, stride=strd, bias=False),
                nn.BatchNorm2d(self.multiplier*num_planes)
            )
    def forward(self, inp):
        op = F.relu(self.batch_norm1(self.conv_layer1(inp)))
        op = self.batch_norm2(self.conv_layer2(op))
        op += self.res_connnection(inp)
        op = F.relu(op)
        return op

[m7mdhka]

Also, this layer have non-identifed variable stride and I think it must be the strd, that make me confused for a while:

        self.conv_layer1 = nn.Conv2d(in_channels=input_num_planes, out_channels=num_planes, kernel_size=3, stride=stride, padding=1, bias=False)