code: def _page_streamable(page_descriptor):
      
  
      def inner(a_func, settings, request, **kwargs):
          """Actual page-streaming based on the settings."""
          page_iterator = gax.PageIterator(
              a_func, page_descriptor, settings.page_token, request, **kwargs)
          if settings.flatten_pages:
              return gax.ResourceIterator(page_iterator)
          else:
              return page_iterator
  
      return inner
docs: Creates a function that yields an iterable to performs page-streaming.
  
      Args:
          page_descriptor (:class:`PageDescriptor`): indicates the structure
            of page streaming to be performed.
  
      Returns:
          Callable: A function that returns an iterator.