code: private CustomVariable getCustomVariable(String parameter, int index){        
          CustomVariableList cvl = (CustomVariableList)parameters.get(parameter);
          if (cvl == null){
              return null;
          }
          
          return cvl.get(index);
      }
docs: Get a value that is stored in a json object at the specified parameter.
  @param parameter the parameter to retrieve the json object from
  @param key the key of the value.  Cannot be null
  @return the value