docs: def _construct_bundling(bundle_config, bundle_descriptor):
      """Helper for ``construct_settings()``.
  
      Args:
        bundle_config (dict): A dictionary specifying a bundle parameters, the
          value for 'bundling' field in a method config (See
          ``construct_settings()`` for information on this config.)
        bundle_descriptor (BundleDescriptor): A BundleDescriptor object
          describing the structure of bundling for this method. If not set,
          this method will not bundle.
  
      Returns:
        Tuple[bundling.Executor, BundleDescriptor]: A tuple that configures
          bundling. The bundling.Executor may be None if this method should not
          bundle.
      """
      if bundle_config and bundle_descriptor:
          bundler = bundling.Executor(gax.BundleOptions(
              element_count_threshold=bundle_config.get(
                  'element_count_threshold', 0),
              element_count_limit=bundle_config.get('element_count_limit', 0),
              request_byte_threshold=bundle_config.get(
                  'request_byte_threshold', 0),
              request_byte_limit=bundle_config.get('request_byte_limit', 0),
              delay_threshold=bundle_config.get('delay_threshold_millis', 0)))
      else:
          bundler = None
  
      return bundler