Prediction: minor fix on ADCJunctionId interface

Author: HongyiSun

modules/prediction/container/storytelling/storytelling_container.cc

@@ -32,7 +32,7 @@ std::shared_ptr<const hdmap::JunctionInfo> StoryTellingContainer::ADCJunction()
   return PredictionMap::JunctionById(adc_junction_id);
 }
 
-std::string StoryTellingContainer::ADCJunctionId() const {
+const std::string& StoryTellingContainer::ADCJunctionId() const {
   return close_to_junction_.junction_id();
 }
 

modules/prediction/container/storytelling/storytelling_container.h

@@ -57,9 +57,9 @@ class StoryTellingContainer : public Container {
 
   /**
    * @brief Get ADC junction id
-   * @return A pointer to ADC junction id
+   * @return A reference of ADC_junction_id
    */
-  std::string ADCJunctionId() const;
+  const std::string& ADCJunctionId() const;
 
   /**
    * @brief Compute ADC's distance to junction