input: Write a function to generate a random password of length 6.
  assert len(generate_password()) == 6
  assert isinstance(generate_password(), str)
  assert any(c.islower() for c in generate_password())
  assert any(c.isupper() for c in generate_password())
  assert any(c.isdigit() for c in generate_password())
output: import random
  import string
  
  def generate_password():
      characters = string.ascii_letters + string.digits
      password = ''.join(random.choice(characters) for _ in range(6))
      return password