code: public Formula naryOperator(final FType type, final Formula... operands) {
      switch (type) {
        case OR:
          return this.or(operands);
        case AND:
          return this.and(operands);
        default:
          throw new IllegalArgumentException("Cannot create an n-ary formula with operator: " + type);
      }
    }
docs: Creates a new n-ary operator with a given type and a list of operands.
  @param type     the type of the formula
  @param operands the list of operands
  @return the newly generated formula
  @throws IllegalArgumentException if a wrong formula type is passed