Convert compatible prelu weights to rank 1 (#2054)

crates/burn-import/src/onnx/to_burn.rs

@@ -974,9 +974,19 @@ impl ParsedOnnxGraph {
     fn prelu_conversion<PS: PrecisionSettings>(node: Node) -> PReluNode {
         let input = TensorType::from(node.inputs.first().unwrap());
         let output = TensorType::from(node.outputs.first().unwrap());
-        let weight = extract_data_serialize::<PS::FloatElem>(1, &node).unwrap();
+        let mut weight = extract_data_serialize::<PS::FloatElem>(1, &node).unwrap();
         let config = PReluConfig::new();
         let name = &node.name;
+
+        if weight.shape.len() > 1 {
+            if weight.shape[1..].iter().product::<usize>() == 1 {
+                // Burn accepts rank 1 alpha weight
+                weight.shape = weight.shape[..1].to_vec();
+            } else {
+                panic!("Invalid PRelu weight with shape {:?}", weight.shape);
+            }
+        }
+
         PReluNode::new(name, input, output, weight, config)
     }
     fn conv_transpose2d_conversion<PS: PrecisionSettings>(node: Node) -> ConvTranspose2dNode {