}

        auto called_index_attr = mlir::dyn_cast_or_null<IntegerAttr>(
            backend_config.get(kCalledIndexAttrName));
        if (!called_index_attr) {
          op->emitOpError()
              << "is missing attribute '" << kCalledIndexAttrName << "'";
          return WalkResult::interrupt();
        }
        int called_index = called_index_attr.getInt();

// i64 attribute `called_index` to the TF function's name.
constexpr llvm::StringRef kTfBackendConfigAttrName = "tf.backend_config";
constexpr llvm::StringRef kCalledIndexAttrName = "called_index";
constexpr llvm::StringRef kCalledFuncAttrName = "called_func";

// Converts `called_func` attributes in custom call ops back to `called_index`.