@property
@abc.abstractmethod
def key_format(self) -> Optional[str]:
    'Return the format for the keys of the repository.\n\n        Important for when migrating between backends (e.g. archive -> main), as if they are not equal then it is\n        necessary to re-compute all the `Node.repository_metadata` before importing (otherwise they will not match\n        with the repository).\n        '
Return the format for the keys of the repository.

Important for when migrating between backends (e.g. archive -> main), as if they are not equal then it is
necessary to re-compute all the `Node.repository_metadata` before importing (otherwise they will not match
with the repository).
@property
@abc.abstractmethod
def key_format(self) -> Optional[str]:
    'Return the format for the keys of the repository.\n\n        Important for when migrating between backends (e.g. archive -> main), as if they are not equal then it is\n        necessary to re-compute all the `Node.repository_metadata` before importing (otherwise they will not match\n        with the repository).\n        '