The USB transport interfaces with a local Bluetooth USB dongle.
The moniker for a USB transport is either usb:<index> or usb:<vendor>:<product> with <index> as the 0-based index to select amongst all the devices that appear to be supporting Bluetooth HCI (0 being the first one), or where <vendor> and <product> are a vendor ID and product ID in hexadecimal.
!!! example usb:04b4:f901
Use the USB dongle with vendor equal to 04b4 and product equal to f901
`usb:0` Use the first Bluetooth dongle
The library includes two different implementations of the USB transport, implemented using different python bindings for libusb. Using the transport prefix pyusb: instead of usb: selects the implementation based on PyUSB, using the synchronous API of libusb, whereas the default implementation is based on libusb1, using the asynchronous API of libusb. In order to use the alternative PyUSB-based implementation, you need to ensure that you have installed that python module, as it isn't installed by default as a dependency of Bumble.