input: Write a function to generate a random string of length 8 made of uppercase letters and numbers.
  assert generate_random_string()=='A8B7C6D5'
  assert generate_random_string()=='X2Y3Z4Q5'
  assert generate_random_string()=='1A2B3C4D'
  assert generate_random_string()=='5E6F7G8H'
  assert generate_random_string()=='Q1W2E3R4'
output: import random
  import string
  
  def generate_random_string():
      return ''.join(random.choices(string.ascii_uppercase + string.digits, k=8))