input: Write a python function to generate a random password of 8 characters using ascii letters.
  assert len(generate_password()) == 8
  assert all(c in string.ascii_letters for c in generate_password())
  assert generate_password() != generate_password()
output: import random
  import string
  
  def generate_password():
      return ''.join(random.choices(string.ascii_letters, k=8))