code: def authenticate(self, username, password):
          
          PraetorianError.require_condition(
              self.user_class is not None,
              "Praetorian must be initialized before this method is available",
          )
          user = self.user_class.lookup(username)
          MissingUserError.require_condition(
              user is not None,
              'Could not find the requested user',
          )
          AuthenticationError.require_condition(
              self._verify_password(password, user.password),
              'The password is incorrect',
          )
          return user
docs: Verifies that a password matches the stored password for that username.
          If verification passes, the matching user instance is returned