def METHOD_NAME(
    self, resource_arn: str, tags_to_add: Dict[str, str], tags_to_remove: List[str]
) -> None:
    try:
        res = self._find_environment_by_arn(resource_arn)
    except KeyError:
        raise ResourceNotFoundException(
            f"Resource not found for ARN '{resource_arn}'."
        )
    for key, value in tags_to_add.items():
        res.tags[key] = value
    for key in tags_to_remove:
        del res.tags[key]