Fix issue with model esrgan-tf2_1

Author: sdpython

tests/run_pretrained_models.yaml

@@ -115,12 +115,22 @@ benchtf-gru:
 ##
 ## standard image nets
 ##
+
+esrgan-tf2:
+  url: https://tfhub.dev/captain-pool/esrgan-tf2/1/esrgan-tf2_1.tar.gz
+  model: fixme
+  input_get: get_beach
+  inputs:
+    "input:0": [1, 416, 416, 3]
+  outputs:
+    - Identity:0
+
 inception_v3_slim:
   url: https://storage.googleapis.com/download.tensorflow.org/models/inception_v3_2016_08_28_frozen.pb.tar.gz
   model: inception_v3_2016_08_28_frozen.pb
   input_get: get_beach
   inputs:
-    "input:0": [1, 299, 299, 3]
+    "input_0:0": [1, 299, 299, 3]
   outputs:
     - InceptionV3/Predictions/Softmax:0
   rtol: 0.02

tf2onnx/optimizer/transpose_optimizer.py

@@ -648,7 +648,10 @@ def _reducemean_handler(self, trans, node):
     def _slice_handler(self, trans, node):
         axes = None
         if self._g.opset < 10:
-            axes = node.get_attr("axes").ints
+            axes_values = node.get_attr("axes")
+            if not axes_values:
+                return False
+            axes = axes_values.ints
             if axes == [0, 1, 2, 3]:
                 node.set_attr("axes", NCHW_TO_NHWC)
                 return self._switch_transpose_and_node(node, trans)