code: @SuppressWarnings("unchecked")
    public <T> T getRequiredValue(String key) {
  
      T value = (T) map.get(key);
      if (value == null) {
        throw new RequiredParameterException();
      }
      return value;
    }
docs: Get a required value from a key out of the Job Context
  
  @param key
  @return