code: public Map<String, String> verifyAndGet() {
          for (String paramName : required) {
              if (params.get(paramName) == null) {
                  throw new IllegalStateException(format("Param %s is required but has not been supplied", paramName));
              }
          }
          return params;
      }
docs: /*
  Verifies that all required parameters have been set
  
  @return a map of the parameters