NMDeviceModem @NM_DEVICE_MODEM_ERROR_UNKNOWN: @NM_DEVICE_MODEM_ERROR_NOT_MODEM_CONNECTION: @NM_DEVICE_MODEM_ERROR_INVALID_MODEM_CONNECTION: @NM_DEVICE_MODEM_ERROR_MISSING_DEVICE_CAPS: @void: @Returns: @self: @Returns: @self: @Returns: