return failure();
  }

  auto f = config.get(kCalledFuncAttrName);
  if (f == nullptr) {
    op.emitOpError() << "does not have attribute '" << kCalledFuncAttrName
                     << "' in its dictionary attribute '"
                     << kTfBackendConfigAttrName << "'";
    return failure();
  }

  if (auto attr = mlir::dyn_cast<FlatSymbolRefAttr>(f)) {
    return attr;
  }

    if (!IsTfFuncCustomCall(op)) {
      return WalkResult::advance();
    }

    auto backend_config =
        op->getAttrOfType<DictionaryAttr>(kTfBackendConfigAttrName);
    if (!backend_config) {
      op->emitOpError() << "is missing attribute '" << kTfBackendConfigAttrName
                        << "'";
      return WalkResult::interrupt();
    }
    auto called_func = mlir::dyn_cast_or_null<SymbolRefAttr>(

          return WalkResult::advance();
        }

        auto backend_config =
            op->getAttrOfType<DictionaryAttr>(kTfBackendConfigAttrName);
        if (!backend_config) {
          op->emitOpError()
              << "is missing attribute '" << kTfBackendConfigAttrName << "'";
          return WalkResult::interrupt();
        }

        auto called_index_attr = mlir::dyn_cast_or_null<IntegerAttr>(