message: Expose underlying devices of a ParallelDevice.
diff: @@ -81,6 +81,11 @@ class ParallelDevice {
  // The number of devices operations run on.
  size_t num_underlying_devices() const { return underlying_devices_.size(); }
  + // The devices operations run on.
  + const std::vector<std::string>& underlying_devices() const {
  + return underlying_devices_;
  + }
  +
  // Takes a description of a single operation being executed on the
  // ParallelDevice, and in turn runs one operation per component device with
  // its corresponding inputs from the input ParallelTensors. Wraps the
  