fix errors and update code based on review comments

Author: mindest

tests/test_backend.py

@@ -1702,10 +1702,10 @@ def test_zeros_like(self):
         _ = tf.identity(res1, name=_TFOUTPUT1)
         self._run_test_case([_OUTPUT, _OUTPUT1], {_INPUT: input_val})
 
-    @check_opset_min_version(9, "isnan")
+    @check_opset_min_version(9, "is_nan")
     def test_isnan(self):
         # only compatible with dtype `float32`
-        x_val1 = np.array([1.0, 2.0, -3.0, -4.0], dtype=np.float32).reshape((2,2))
+        x_val1 = np.array([1.0, 2.0, -3.0, -4.0], dtype=np.float32).reshape((2, 2))
         x_val2 = np.array([np.nan, np.nan, np.nan, np.nan], dtype=np.float32).reshape((2, 2))
         x_val3 = np.array([1.0, np.nan, -3.0, np.nan], dtype=np.float32).reshape((2, 2))
         for x_val in [x_val1, x_val2, x_val3]:

tf2onnx/tfonnx.py

@@ -1894,18 +1894,19 @@ def where_op(ctx, node, name, args):
 }
 
 _OPSET_9 = {
-    "Erf": (direct_op, []),
-    "Fill": (fill_op, []),
-    "Sinh": (direct_op, []),
-    "Cosh": (direct_op, []),
-    "Asinh": (direct_op, []),
     "Acosh": (direct_op, []),
+    "Asinh": (direct_op, []),
     "Atanh": (direct_op, []),
+    "Cosh": (direct_op, []),
+    "Erf": (direct_op, []),
+    "Fill": (fill_op, []),
     "Greater": (logical_compare_op, []),
+    "IsNan": (direct_op, ["IsNaN"])
     "Less": (logical_compare_op, []),
     "ResizeBilinear": (upsample_op9, ["Upsample", "linear"]),
     "ResizeNearestNeighbor": (upsample_op9, ["Upsample", "nearest"]),
     "Where": (where_op, []),
+    "Sinh": (direct_op, []),
 }
 
 _OPSETS = [