code: def _check_user(self, user):
          
          MissingUserError.require_condition(
              user is not None,
              'Could not find the requested user',
          )
          user_validate_method = getattr(
              user, self.user_class_validation_method, None
          )
          if user_validate_method is None:
              return
          InvalidUserError.require_condition(
              user_validate_method(),
              "The user is not valid or has had access revoked",
          )
docs: Checks to make sure that a user is valid. First, checks that the user
          is not None. If this check fails, a MissingUserError is raised. Next,
          checks if the user has a validation method. If the method does not
          exist, the check passes. If the method exists, it is called. If the
          result of the call is not truthy, an InvalidUserError is raised