Currently, find_batched() has the following signature:

def find_batched(
    ...
) -> List[FindResult]:

In order to align with DocumentIndex, it should be switched to:

def find_batched(
    ...
) -> FindResultBatched:

TODOs:

• move the definition of FindResultBatched from index/abstract.py to utils/find.py
• change the signature as described above
• fix the imports on all Document Index classes
• Probably FindResultBatched needs a tweak as well: scores: np.ndarray probably needs to be changed to allow a union of ndarray, torch.Tensor and tf.Tensor