docs: public Rational pow(int exponent) {
          if (exponent == 0) {
              return new Rational(1, 1);
          }
          BigInteger num = a.pow(Math.abs(exponent));
          BigInteger deno = b.pow(Math.abs(exponent));
          if (exponent > 0) {
              return (new Rational(num, deno));
          } else {
              return (new Rational(deno, num));
          }
      }