sub apply_to {
my ($self, $old_hyp) = @_;
trace 'step.apply.old_hyp '.$self => $old_hyp;
+ trace 'step.apply.actions '.$self => $self->actions;
my $new_hyp = $self->_apply_to_hyp($old_hyp);
return (undef, $self->alternative_step) unless $new_hyp;
trace 'step.apply.new_hyp '.$self => $new_hyp;