add pt2tf tool

pt2tf/onnx-tensorflow/onnx_tf/handlers/backend/is_nan.py

@@ -0,0 +1,14 @@
+import tensorflow as tf
+
+from onnx_tf.handlers.backend_handler import BackendHandler
+from onnx_tf.handlers.handler import onnx_op
+from onnx_tf.handlers.handler import tf_func
+
+
+@onnx_op("IsNaN")
+@tf_func(tf.is_nan)
+class IsNaN(BackendHandler):
+
+  @classmethod
+  def version_9(cls, node, **kwargs):
+    return [cls.make_tensor_from_onnx_node(node, **kwargs)]