docs: def __verify_username(self, username):
          """Raises an exception if the given username is not valid."""
  
          if len(username) > self.__max_length or len(username) < 3:
              raise ValueError(
                  f"Username must be between 3 and {self.__max_length} characters."
              )
          if any(c not in string.ascii_letters + string.digits for c in username):
              raise ValueError("Usernames can only contain alphanumeric characters.")