input: Write a python function to generate 6 unique random lottery numbers between 1 and 49.
  assert len(generate_lottery_numbers()) == 6
  assert all(1 <= num <= 49 for num in generate_lottery_numbers())
  assert len(set(generate_lottery_numbers())) == 6
output: import random
  
  def generate_lottery_numbers():
      return random.sample(range(1, 50), 6)