def METHOD_NAME(self, fd, fdset, opaque, opts=''):
    '''Pass a file descriptor to the VM'''
    options = ['fd=%d' % fd,
               'set=%d' % fdset,
               'opaque=%s' % opaque]
    if opts:
        options.append(opts)
    self._args.append('-add-fd')
    self._args.append(','.join(options))
    return self