tuned proof (no induction needed); removed unused lemma and fuzzy comment
tuned proof (no induction needed); removed unused lemma and fuzzy comment

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle