'Returns True iff the _is_device_mtp check returns True and libmtp
is able to probe the device successfully.'

def is_device_mtp(self, d, debug=None):

    if (self._is_device_mtp is None):
        return False
    return (self._is_device_mtp(d, debug=debug) and self.libmtp.is_mtp_device(d.busnum, d.devnum))
