def METHOD_NAME(
        self, resource_group_name, virtual_wan_name, output_blob_sas_url, vpn_sites=None, custom_headers=None, raw=False, polling=True, **operation_config):
    """Gives the sas-url to download the configurations for vpn-sites in a
    resource group.
    :param resource_group_name: The resource group name.
    :type resource_group_name: str
    :param virtual_wan_name: The name of the VirtualWAN for which
     configuration of all vpn-sites is needed.
    :type virtual_wan_name: str
    :param output_blob_sas_url: The sas-url to download the configurations
     for vpn-sites.
    :type output_blob_sas_url: str
    :param vpn_sites: List of resource-ids of the vpn-sites for which
     config is to be downloaded.
    :type vpn_sites: list[str]
    :param dict custom_headers: headers that will be added to the request
    :param bool raw: The poller return type is ClientRawResponse, the
     direct response alongside the deserialized response
    :param polling: True for ARMPolling, False for no polling, or a
     polling object for personal polling strategy
    :return: An instance of LROPoller that returns None or
     ClientRawResponse<None> if raw==True
    :rtype: ~msrestazure.azure_operation.AzureOperationPoller[None] or
     ~msrestazure.azure_operation.AzureOperationPoller[~msrest.pipeline.ClientRawResponse[None]]
    :raises:
     :class:`ErrorException<azure.mgmt.network.v2019_06_01.models.ErrorException>`
    """
    raw_result = self._download_initial(
        resource_group_name=resource_group_name,
        virtual_wan_name=virtual_wan_name,
        output_blob_sas_url=output_blob_sas_url,
        vpn_sites=vpn_sites,
        custom_headers=custom_headers,
        raw=True,
        **operation_config
    )
    def get_long_running_output(response):
        if raw:
            client_raw_response = ClientRawResponse(None, response)
            return client_raw_response
    lro_delay = operation_config.get(
        'long_running_operation_timeout',
        self.config.long_running_operation_timeout)
    if polling is True: polling_method = ARMPolling(lro_delay, lro_options={'final-state-via': 'location'}, **operation_config)
    elif polling is False: polling_method = NoPolling()
    else: polling_method = polling
    return LROPoller(self._client, raw_result, get_long_running_output, polling_method)