Clarified opset import and supported onnx versions

lib/nir/node.mli

@@ -28,7 +28,7 @@
     - a node description of type [descr]
 
     [descr] describes several operations. Most of them are direct transcription
-    of the ONNX v13 standard, which a description is available here:
+    of the ONNX IR v8 standard, which a description is available here:
     https://onnx.ai/onnx/operators/index.html.
 
     Nodes only require their inputs: it is assumed that a node only returns one

lib/onnx/writer.ml

@@ -58,7 +58,7 @@ let convert_into_tensor ?name (t : Nir.Gentensor.t) =
 let default_opset_import =
   let open Oproto.Onnx in
   let onnx_domain = "" in
-  OperatorSetIdProto.make ~domain:onnx_domain ~version:8L ()
+  OperatorSetIdProto.make ~domain:onnx_domain ~version:22L ()
 
 let nier_simple_to_onnx_protoc (nier_simple : Nir.Ngraph.t) =
   let open Oproto.Onnx in