code: @SuppressWarnings("unchecked")
      public Map<String, Object> getParamMap(String paramName) {
          Object paramValue = getParam(paramName);
          if (paramValue == null) {
              return null;
          }
          if (!(paramValue instanceof Map)) {
              throw new IllegalArgumentException("Parameter '" + paramName + "' must be a map: " + paramValue);
          }
          return (Map<String, Object>)paramValue;
      }
docs: Get the value of the given parameter name as a Map. If no such parameter name is
  known, null is returned. If the parameter is defined but is not a Map, an
  IllegalArgumentException is thrown.
  
  @param paramName     Name of parameter to get value of.
  @return              Parameter value as a String/Objec Map or null if unknown.