Show error when using keras2onnx with tf>=2.3 (#116)

* Show error when using keras2onnx with tf>=2.3

* Change warn flag to raise; update message

* Using f string

Author: natuan

src/sparseml/keras/utils/exporter.py

@@ -60,6 +60,7 @@ def export_onnx(
         opset: int = DEFAULT_ONNX_OPSET,
         doc_string: str = "",
         debug_mode: bool = True,
+        raise_on_tf_support: bool = True,
         **kwargs,
     ):
         """
@@ -74,6 +75,16 @@ def export_onnx(
         if keras2onnx_import_error is not None:
             raise keras2onnx_import_error
 
+        if raise_on_tf_support:
+            import tensorflow
+            v = tensorflow.__version__
+            if v >= "2.3.0":
+                raise ValueError(
+                    f"Tensorflow version {v} is greater than the currently supported "
+                    "version for keras2onnx. Please downgrade the Tensorflow <2.3.0 "
+                    "or set raise_on_tf_support to False to continue."
+                )
+
         model_name = self._model.name or name.split(".onnx")[0]
         onnx_model = keras2onnx.convert_keras(
             self._model,