const std::string& filename, int64_t file_signature) {
  absl::MutexLock lock(&mu_);
  auto it = file_signature_map_.find(filename);
  if (it != file_signature_map_.end()) {
    if (it->second == file_signature) {
      return true;
    }
    // Remove the file from cache if the signatures don't match.
    RemoveFile_Locked(filename);
    it->second = file_signature;
    return false;
  }

  CSession csession(session);

  // Retrieve the regression signature from meta graph def.
  const auto signature_def_map = metagraph_def.signature_def();
  const auto signature_def = signature_def_map.at("regress_x_to_y");

  const string input_name =
      signature_def.inputs().at(tensorflow::kRegressInputs).name();
  const string output_name =
      signature_def.outputs().at(tensorflow::kRegressOutputs).name();

    Name("TestCommUnavailable").Device(tensorflow::DEVICE_DEFAULT),
    TestUnavailableErrorOp);

string FunctionWithErrorOp(const tensorflow::StringPiece op_name) {
  const std::string& func_str =
      "    signature {"
      "      name: 'FunctionWith__OP_NAME__'"
      "      output_arg {"
      "        name: 'out'"
      "        type: DT_STRING"
      "      }"
      "    }"
      "    node_def {"

               char* buffer, TF_Status* status);

  // Validate the given file signature with the existing file signature in the
  // cache. Returns true if the signature doesn't change or the file doesn't
  // exist before. If the signature changes, update the existing signature with
  // the new one and remove the file from cache.
  bool ValidateAndUpdateFileSignature(const std::string& filename,

  ASSERT_EQ(func_->record->fdef().signature().attr().size(), 2);
  EXPECT_EQ(func_->record->fdef().signature().attr(0).name(), "v1");
  EXPECT_EQ(func_->record->fdef().signature().attr(0).type(), "int");
  EXPECT_EQ(func_->record->fdef().signature().attr(1).name(), "v2");
  EXPECT_EQ(func_->record->fdef().signature().attr(1).type(), "int");
}

  // Second read. Hit cache.
  EXPECT_TRUE(cache.ValidateAndUpdateFileSignature(filename, 123));
  TF_EXPECT_OK(ReadCache(&cache, filename, 0, 16, &out));
  EXPECT_EQ(calls, 1);

  // Third read. File signatures are different.
  EXPECT_FALSE(cache.ValidateAndUpdateFileSignature(filename, 321));
  TF_EXPECT_OK(ReadCache(&cache, filename, 0, 16, &out));
  EXPECT_EQ(calls, 2);
}

TEST(RamFileBlockCacheTest, PassThrough) {

  GraphErrorInjectionPass::enabled_ = false;
}

string VariableAddFunctionWithGraphError() {
  string signature = VariableAddFunctionSignature();
  // Replace the node 'read0' with 'read0_maybe_with_graph_error', so that the
  // error injecting pass can identify and introduce graph pass errors.
  signature = std::regex_replace(signature, std::regex("read0"),
                                 "read0_maybe_with_graph_error");

  if (TF_GetCode(status) != TF_OK) return;

  tensorflow::GradientDef gdef;
  gdef.set_function_name(func->record->fdef().signature().name());
  gdef.set_gradient_func(grad->record->fdef().signature().name());
  status->status = g->graph.AddGradientDef(std::move(gdef));
}

int TF_GraphNumFunctions(TF_Graph* g) {
  tensorflow::mutex_lock l(g->mu);

  virtual Status RegisterFunction(AbstractFunction*) = 0;
  // Remove a function. 'func' argument is the name of a previously added
  // FunctionDef. The name is in fdef.signature.name.
  virtual Status RemoveFunction(const string& func) = 0;

 private:
  const AbstractContextKind kind_;
};

namespace internal {
struct AbstractContextDeleter {

      return tensorflow::errors::InvalidArgument("Unsupported Type Codes: ",
                                                 dtype.code);
  }
}

// Wraps the deleter function of DLManagedTensor to match the function signature
// TFE_NewTensorHandleFromDeviceMemory.
void DeallocatorWrapperFunc(void* data, size_t len, void* dlmt_vptr) {
  TFE_CallDLManagedTensorDeleter(dlmt_vptr);
}