input: Write a function to generate a random password consisting of 8 characters. The function should use a combination of uppercase letters, lowercase letters, and digits. If there is no input, the function should return the generated password.
  assert generate_password()==any
output: import random
  import string
  
  def generate_password():
      characters = string.ascii_letters + string.digits
      return ''.join(random.choice(characters) for _ in range(8))