code: def _get_usb_device(self, skip=0):
          
          try:
              # PyUSB >= 1.0, this is a workaround for a problem with libusbx
              # on Windows.
              import usb.core
              import usb.legacy
              devices = [usb.legacy.Device(d) for d in usb.core.find(
                  find_all=True, idVendor=YUBICO_VID)]
          except ImportError:
              # Using PyUsb < 1.0.
              import usb
              devices = [d for bus in usb.busses() for d in bus.devices]
          for device in devices:
              if device.idVendor == YUBICO_VID:
                  if device.idProduct in PID.all(otp=True):
                      if skip == 0:
                          return device
                      skip -= 1
          return None
docs: Get YubiKey USB device.
  
          Optionally allows you to skip n devices, to support multiple attached YubiKeys.