replace 'residual' with 'identity' (#338)

maskrcnn_benchmark/modeling/backbone/resnet.py

@@ -250,7 +250,7 @@ class BottleneckWithFixedBatchNorm(nn.Module):
         self.bn3 = FrozenBatchNorm2d(out_channels)
 
     def forward(self, x):
-        residual = x
+        identity = x
 
         out = self.conv1(x)
         out = self.bn1(out)
@@ -264,9 +264,9 @@ class BottleneckWithFixedBatchNorm(nn.Module):
         out = self.bn3(out0)
 
         if self.downsample is not None:
-            residual = self.downsample(x)
+            identity = self.downsample(x)
 
-        out += residual
+        out += identity
         out = F.relu_(out)
 
         return out