bugfix sequence explanations

Author: larsbengel

org-tweetyproject-arg-dung/src/main/java/org/tweetyproject/arg/dung/serialisability/semantics/SerialisationSequence.java

@@ -87,7 +87,7 @@ public Extension<DungTheory> getExtension() {
 
     @Override
     public int size() {
-        return arguments.size();
+        return sequence.size();
     }
 
     @Override

org-tweetyproject-arg-explanations/src/main/java/org/tweetyproject/arg/explanations/reasoner/acceptance/DialecticalSequenceExplanationReasoner.java

@@ -67,7 +67,7 @@ public Collection<Explanation> getExplanations(DungTheory theory, Argument argum
     private Collection<Argument> getDefeated(DungTheory theory, SerialisationSequence seq, Argument a, Collection<Argument> s) {
         Collection<Argument> relevantAttackers = new HashSet<>();
         relevantAttackers.addAll(theory.getAttackers(a));
-        relevantAttackers.addAll(seq.getExtension());
+        relevantAttackers.addAll(theory.getAttackers(seq.getExtension()));
         DungTheory reduct = theory.getReduct(new SerialisationSequence(seq.subList(0, seq.indexOf(s))).getExtension());
         Collection<Argument> attacked = new HashSet<>(reduct.getAttacked(s));
         relevantAttackers.retainAll(attacked);