sub set_wakeup_callback {
    my ($self, $callback, $userdata) = @_;
    $self->set_my_callback($callback);
    #$self->set_callback_data($userdata);
    #use Devel::Peek;
    #Dump $callback;
    $self->_xs_set_wakeup_callback();
    #use Devel::Peek;
    #Dump $callback;
}