code: public String getAsSimpleString() {
          String rewardString = "";
          for (Map.Entry<Integer, Float> entry : this.map.entrySet()) {
              Integer dimension = entry.getKey();
              Float reward_value = entry.getValue();
              if (!rewardString.isEmpty())
                  rewardString += ",";
              rewardString += dimension + ":" + reward_value;
          }
          return rewardString;
      }
docs: Gets the reward structure as a simple, easily parsed string<br>
  Format: <dimension>:<value>, comma delimited.
  eg "0:45.6,1:32.2,12:-1.0" etc
  
  @return the string.