code: void addClauseSet(final Formula formula, final Proposition proposition) {
          switch (formula.type()) {
              case TRUE:
                  break;
              case FALSE:
              case LITERAL:
              case OR:
                  this.addClause(formula, proposition);
                  break;
              case AND:
                  for (final Formula op : formula) { this.addClause(op, proposition); }
                  break;
              default:
                  throw new IllegalArgumentException("Input formula ist not a valid CNF: " + formula);
          }
      }
docs: Adds a formula which is already in CNF to the solver.
  @param proposition a proposition (if required for proof tracing)
  @param formula     the formula in CNF