def start_extension_upgrade(<EOL>self, resource_group_name, vm_scale_set_name, custom_headers=None, raw=False, polling=True, **operation_config):
raw_result = self._start_extension_upgrade_initial(<EOL>resource_group_name=resource_group_name,<EOL>vm_scale_set_name=vm_scale_set_name,<EOL>custom_headers=custom_headers,<EOL>raw=True,<EOL>**operation_config<EOL>)<EOL>def get_long_running_output(response):<EOL><INDENT>if raw:<EOL><INDENT>client_raw_response = ClientRawResponse(None, response)<EOL>return client_raw_response<EOL><DEDENT><DEDENT>lro_delay = operation_config.get(<EOL>'<STR_LIT>',<EOL>self.config.long_running_operation_timeout)<EOL>if polling is True: polling_method = ARMPolling(lro_delay, **operation_config)<EOL>elif polling is False: polling_method = NoPolling()<EOL>else: polling_method = polling<EOL>return LROPoller(self._client, raw_result, get_long_running_output, polling_method)<EOL>
Starts a rolling upgrade to move all extensions for all virtual machine
        scale set instances to the latest available extension version.
        Instances which are already running the latest extension versions are
        not affected.

        :param resource_group_name: The name of the resource group.
        :type resource_group_name: str
        :param vm_scale_set_name: The name of the VM scale set.
        :type vm_scale_set_name: 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:`CloudError<msrestazure.azure_exceptions.CloudError>`