def usb_file_system_subscribe_cb()

in usb_monitor_pkg/usb_monitor_pkg/usb_monitor_node.py [0:0]


    def usb_file_system_subscribe_cb(self, req, res):
        """Callback for the usb_file_system_subscribe service. Adds the file/folder details
           to the subscriber list.

        Args:
            req (USBFileSystemSubscribeSrv.Request): Request object with file_name(str),
                                                     callback_name(str) and
                                                     verify_name_exists(bool) flag to be
                                                     added to the subscriber list.
            res (USBFileSystemSubscribeSrv.Response): Response object with error(int) flag
                                                      to indicate if the service call was
                                                      successful.

        Returns:
            USBFileSystemSubscribeSrv.Response: Response object with error(int) flag to
                                                indicate if the service call was successful.
        """
        self.subscribers.append((req.file_name, req.callback_name, req.verify_name_exists))
        res.error = 0
        self.get_logger().info("USB File system subscription : "
                               f"{req.file_name} "
                               f"{req.callback_name} "
                               f"{req.verify_name_exists}")
        return res