Export single output only (ultralytics#7259)

* Update

* Update

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

export.py

@@ -477,6 +477,7 @@ def run(
         if isinstance(m, Detect):
             m.inplace = inplace
             m.onnx_dynamic = dynamic
+            m.export = True
             if hasattr(m, 'forward_export'):
                 m.forward = m.forward_export  # assign custom forward (optional)
 

models/yolo.py

@@ -37,6 +37,7 @@
 class Detect(nn.Module):
     stride = None  # strides computed during build
     onnx_dynamic = False  # ONNX export parameter
+    export = False  # export mode
 
     def __init__(self, nc=80, anchors=(), ch=(), inplace=True):  # detection layer
         super().__init__()
@@ -72,7 +73,7 @@ def forward(self, x):
                     y = torch.cat((xy, wh, conf), 4)
                 z.append(y.view(bs, -1, self.no))
 
-        return x if self.training else (torch.cat(z, 1), x)
+        return x if self.training else (torch.cat(z, 1),) if self.export else (torch.cat(z, 1), x)
 
     def _make_grid(self, nx=20, ny=20, i=0):
         d = self.anchors[i].device