error importing sam2

I get error with following lines:
`from sam2.build_sam import build_sam2`
`from sam2.sam2_image_predictor import SAM2ImagePredictor`
the message says：Unresolved reference 'sam2'
I have already excuted the command : `pip install -e ".[notebooks]"`
but I still can not import the package “sam2”

and another question，why is the root directory doesn't contain __init__.py，is this the reason？

could you please help？thanks

Reproduce the import issue after running `pip install -e ".[notebooks]"`, using the imports `sam2.build_sam` and `sam2.sam2_image_predictor` mentioned in the report. Inspect whether the repository layout and missing root `__init__.py` explain the unresolved reference. Done means identifying the required setup or confirming a project-side correction.

Written by the indexing model from the issue text.