add pt2tf tool

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

@@ -0,0 +1,20 @@
+import tensorflow as tf
+
+from onnx_tf.handlers.backend_handler import BackendHandler
+from onnx_tf.handlers.handler import onnx_op
+
+
+@onnx_op("BitShift")
+class BitShift(BackendHandler):
+
+  @classmethod
+  def _common(cls, node, **kwargs):
+    tf_func = tf.bitwise.left_shift if node.attrs.get(
+        "direction") == "LEFT" else tf.bitwise.right_shift
+    return [
+        cls.make_tensor_from_onnx_node(node, tf_func=tf_func, **kwargs)
+    ]
+
+  @classmethod
+  def version_11(cls, node, **kwargs):
+    return cls._common(node, **kwargs)