code: def _merge_retry_options(retry_options, overrides):
      
      if overrides is None:
          return None
  
      if overrides.retry_codes is None and overrides.backoff_settings is None:
          return retry_options
  
      codes = retry_options.retry_codes
      if overrides.retry_codes is not None:
          codes = overrides.retry_codes
      backoff_settings = retry_options.backoff_settings
      if overrides.backoff_settings is not None:
          backoff_settings = overrides.backoff_settings
  
      return gax.RetryOptions(
          backoff_settings=backoff_settings,
          retry_codes=codes,
      )
docs: Helper for ``construct_settings()``.
  
      Takes two retry options, and merges them into a single RetryOption instance.
  
      Args:
        retry_options (RetryOptions): The base RetryOptions.
        overrides (RetryOptions): The RetryOptions used for overriding ``retry``.
          Use the values if it is not None. If entire ``overrides`` is None,
          ignore the base retry and return None.
  
      Returns:
        RetryOptions: The merged options, or None if it will be canceled.