fix backward

paddle/framework/backward.cc

@@ -79,9 +79,9 @@ std::shared_ptr<OperatorBase> BackwardRecursive(
   //  All output gradients of forwarding operator do not need to calculate.
   //  Then all input gradients cannot be computed at all, and we put them into
   //  `no_grad_names` set. Return an NOP.
-  if (AllInSet(forwardOp.Output() /*names*/, kGradVarSuffix /*suffix*/,
+  if (AllInSet(forwardOp.Outputs() /*names*/, kGradVarSuffix /*suffix*/,
                no_grad_names /*set*/)) {
-    ForEachVarName(forwardOp.inputs_,
+    ForEachVarName(forwardOp.Inputs(),
                    [&no_grad_names](const std::string& name) -> bool {
                      no_grad_names.insert(GradVarName(name));
                      return false;