input: Write a python function to add two fractions using a class method.
  assert Fraction(1, 2).add(Fraction(1, 3)) == (5, 6)
  assert Fraction(3, 4).add(Fraction(2, 5)) == (23, 20)
  assert Fraction(5, 6).add(Fraction(1, 6)) == (1, 1)
output: def gcd(a, b):
      while b:
          a, b = b, a % b
      return a
  
  class Fraction:
      def __init__(self, numerator, denominator):
          self.numerator = numerator
          self.denominator = denominator
  
      def add(self, other):
          new_numerator = self.numerator * other.denominator + other.numerator * self.denominator
          new_denominator = self.denominator * other.denominator
          common_divisor = gcd(new_numerator, new_denominator)
          return (new_numerator // common_divisor, new_denominator // common_divisor)