fix: unsqueeze axes became an input in onnx op set v13 (#93)

dnnv/nn/operations/tensor.py

@@ -247,12 +247,19 @@ def __init__(self, x, axes, *, name: Optional[str] = None):
     @classmethod
     def from_onnx(cls, onnx_node, *inputs):
         attributes = {a.name: as_numpy(a) for a in onnx_node.attribute}
-        axes = attributes.get("axes")
         if isinstance(inputs[0], np.ndarray):
-            a = inputs[0]
-            for axis in axes:
-                a = np.expand_dims(a, axis)
-            return a
+            if len(inputs) == 2:
+                axes = inputs[1]
+            else:
+                axes = attributes["axes"]
+            if not isinstance(axes, Operation):
+                a = inputs[0]
+                for axis in axes:
+                    a = np.expand_dims(a, axis)
+                return a
+        if len(inputs) == 2:
+            return cls(*inputs, name=onnx_node.name)
+        axes = attributes["axes"]
         return cls(*inputs, axes=axes, name=onnx_node.name)