code: public void checkRequired(String key) throws InitializationFailedException {
      if (properties.get(key) == null && getConfigurationValue(key) == null) {
        throw new InitializationFailedException("Missing required property in config: " + key);
      }
    }
docs: Checks if a property value for a given key exists.
  
  @param key
  property name
  @throws InitializationFailedException
  throw when a given property is not defined