code: public Plan getPlan(final String planCode) {
          if (planCode == null || planCode.isEmpty())
              throw new RuntimeException("planCode cannot be empty!");
  
          return doGET(Plan.PLANS_RESOURCE + "/" + planCode, Plan.class);
      }
docs: Get a Plan's details
  <p>
  
  @param planCode recurly id of plan
  @return the plan object as identified by the passed in ID