[Experiment] faill to mutate expression while converting LSTM

* ExprMutator without any change fails to mutate expressions during
  converting LSTM
* [1]apache#9723 (comment)
* [2]https://github.com/apache/tvm/blob/122be3fb18902bf2317797fedfa867dcf9607ef9/src/relay/transforms/de_duplicate.cc#L113
* [3] https://github.com/apache/tvm/blob/8f6fa8f2c41406cb54d01647ba8731e4ceb8f4ab/src/ir/module.cc#L202
* [4] https://github.com/apache/tvm/blob/8f6fa8f2c41406cb54d01647ba8731e4ceb8f4ab/python/tvm/relay/expr_functor.py#L216
* [5]apache#10072
* [6]apache#9723 (comment)
* [7]https://github.com/apache/tvm/blob/8f6fa8f2c41406cb54d01647ba8731e4ceb8f4ab/src/relay/transforms/de_duplicate.cc

python/tvm/relay/frontend/pytorch.py

@@ -3402,6 +3402,21 @@ def _handel_nested_input(inputs):
                 relay_out = relay_op(
                     inputs, _get_input_types(op_node, outputs, default_dtype=self.default_dtype)
                 )
+
+                def do_mutate(sym):
+                    class PureMutator(ExprMutator):
+                        def __init__(self):
+                            ExprMutator.__init__(self)
+
+                        def mutate(self, sym):
+                            if isinstance(sym, _expr.TupleWrapper):
+                                return _expr.TupleWrapper(self.visit(sym.tuple_value), sym.size)
+                            if isinstance(sym, _expr.RelayExpr):
+                                return self.visit(sym)
+                            return sym
+                    return PureMutator().mutate(sym)
+
+                relay_out = do_mutate(relay_out)
                 self.record_output_type(relay_out)
 
                 if isinstance(relay_out, tuple):