style(models): fix style error (#1566)

.github/workflows/ci.yaml

@@ -13,7 +13,7 @@ jobs:
   # This workflow contains a single job called "build"
   build:
     # The type of runner that the job will run on
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         python-version: [3.6, 3.7, 3.8]

yolox/models/yolo_head.py

@@ -246,7 +246,11 @@ class YOLOXHead(nn.Module):
         grids = torch.cat(grids, dim=1).type(dtype)
         strides = torch.cat(strides, dim=1).type(dtype)
 
-        outputs = torch.cat([(outputs[..., 0:2] + grids) * strides, torch.exp(outputs[..., 2:4]) * strides, outputs[..., 4:]], dim=-1)
+        outputs = torch.cat([
+            (outputs[..., 0:2] + grids) * strides,
+            torch.exp(outputs[..., 2:4]) * strides,
+            outputs[..., 4:]
+        ], dim=-1)
         return outputs
 
     def get_losses(