Explain to me why my password generator code wont run...

**password_generator.py** <br>```python<br>import random<br>import string<br>class PasswordGenerator:<br> def __init__(self):<br> self.name = 'password_generator'<br><br> def generate_password(self):<br> length = 12<br> upper, lower, letters, punctuation, digits = True, True, True, True, True<br> all = string.ascii_letters + string.digits + string.punctuation<br> if upper:<br> all += string.ascii_uppercase<br> if lower:<br> all += string.ascii_lowercase<br> if letters:<br> all += string.ascii_letters<br> if punctuation:<br> all += string.punctuation<br> if digits:<br> all += string.digits<br> if length < 8:<br> print("Password length should be at least 8 characters.")<br> return None<br> password = ''.join(random.choice(all) for i in range(length))<br> return password<br><br>def main():<br> password = PasswordGenerator()<br> print('Generated Password : ' + password.generate_password())<br><br>if __name__ == "__main__":<br> main()<br>```<br>Thanks in advance.