private List<Chain> createChainsFromClauses(Set<Clause> clauses) {
List<Chain> chains = new ArrayList<Chain>();
for (Clause c : clauses) {
Chain chn = new Chain(c.getLiterals());
chn.setProofStep(new ProofStepChainFromClause(chn, c));
chains.add(chn);
chains.addAll(chn.getContrapositives());
}
return chains;