input: Write a function to generate a random password of 8 characters consisting of letters and digits. The function should not take any input and should return the generated password as a string.
  assert generate_password()==any_8_character_password_with_letters_and_digits
  assert generate_password()!=any_8_character_password_with_letters_and_digits_different
output: import random
  import string
  
  def generate_password():
      return ''.join(random.choices(string.ascii_letters + string.digits, k=8))