message: Change string to std::string
diff: @@ -26,9 +26,9 @@ limitations under the License.
  // directives can be embedded into the same file as the source.
  TEST(SavedModel, HalfPlusTwo) {
  const char kSavedModel[] = "cc/saved_model/testdata/half_plus_two/00000123";
  - const string saved_model_dir = tensorflow::io::JoinPath(
  + const std::string saved_model_dir = tensorflow::io::JoinPath(
  tensorflow::testing::TensorFlowSrcRoot(), kSavedModel);
  - std::unordered_set<string> tags{tensorflow::kSavedModelTagServe};
  + std::unordered_set<std::string> tags{tensorflow::kSavedModelTagServe};
  mlir::MLIRContext context;
  auto module = tensorflow::SavedModelToMlirImport(
  