Queues the config sources to be read later (when config is accessed), or reads immediately if config has already been
          accessed.

          :param file/str/list sources: Config source URL (http/https), source string, file name, or file pointer, or list
                                        of the other sources.  If file source does not exist, it is ignored.
          :param int cache_duration: Default cache durationg for for URL source only. Optionally cache the URL content
                                     for the given duration (seconds) to avoid downloading too often.
                                     This sets the default for all reads now and subsequent reads.
          :return: True if all sources were successfully read or will be read, otherwise False

def read(self, sources, cache_duration=None):
        """
          Queues the config sources to be read later (when config is accessed), or reads immediately if config has already been
          accessed.

          :param file/str/list sources: Config source URL (http/https), source string, file name, or file pointer, or list
                                        of the other sources.  If file source does not exist, it is ignored.
          :param int cache_duration: Default cache durationg for for URL source only. Optionally cache the URL content
                                     for the given duration (seconds) to avoid downloading too often.
                                     This sets the default for all reads now and subsequent reads.
          :return: True if all sources were successfully read or will be read, otherwise False
        """
        if cache_duration is not None:
            self._cache_duration = cache_duration

        return super(RemoteConfig, self).read(sources)