@ptrblck , Here is the definition of ResidualBlock:
class ResidualBlock(nn.Module):
    def __init__(self, in_features, use_dropout):
        # super(ResidualBlock, self).__init__()
        super().__init__()
        conv_block = [nn.ReflectionPad2d(1),
                      nn.Conv2d(in_features, in_features, 3, padding=0),
                      nn.InstanceNorm2d(in_features),
                      nn.ReLU(inplace=True),
                      nn.ReflectionPad2d(1),
                      nn.Conv2d(in_features, in_features, 3, padding=0),
                      nn.InstanceNorm2d(in_features)]
        if use_dropout:
            conv_block.insert(4, nn.Dropout(0.5))

        self.conv_block = nn.Sequential(*conv_block)

    def forward(self, x):
        return x + self.conv_block(x)