Add sigmoid_focal_loss, deform_conv2d, get_onnxruntime_op_path to shim

These are imported by mmdet during module loading and must be
available even if not used at inference time.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

setup_mmcv_shim.py

@@ -106,6 +106,28 @@ def rel_roi_point_to_rel_img_point(*args, **kwargs):
 
 def nms_match(*args, **kwargs):
     raise NotImplementedError("nms_match not available in CPU shim")
+
+def sigmoid_focal_loss(input, target, gamma=2.0, alpha=0.25, weight=None, reduction="mean"):
+    p = torch.sigmoid(input)
+    ce_loss = torch.nn.functional.binary_cross_entropy_with_logits(input, target, reduction="none")
+    p_t = p * target + (1 - p) * (1 - target)
+    loss = ce_loss * ((1 - p_t) ** gamma)
+    if alpha >= 0:
+        alpha_t = alpha * target + (1 - alpha) * (1 - target)
+        loss = alpha_t * loss
+    if weight is not None:
+        loss = loss * weight
+    if reduction == "mean":
+        return loss.mean()
+    elif reduction == "sum":
+        return loss.sum()
+    return loss
+
+def deform_conv2d(*args, **kwargs):
+    raise NotImplementedError("deform_conv2d not available in CPU shim")
+
+def get_onnxruntime_op_path():
+    return ""
 '''
 
 with open(os.path.join(ops_dir, '__init__.py'), 'w') as f: