input: Write a function to initialize a multiplication quiz with a given number of questions and generate random questions.
  assert len(MultiplicationQuiz(5).generate_quiz()) == 5
  assert len(MultiplicationQuiz(3).generate_quiz()) == 3
  assert len(MultiplicationQuiz(0).generate_quiz()) == 0
output: import random
  
  class MultiplicationQuiz:
      def __init__(self, num_questions):
          self.num_questions = num_questions
  
      def generate_quiz(self):
          questions = []
          for _ in range(self.num_questions):
              a = random.randint(1, 10)
              b = random.randint(1, 10)
              questions.append((a, b))
          return questions