Add support for nebula graph database

[guzhu271]

Description

[Briefly describe the changes made in this pull request.]

Related Issues

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Changes Made

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Checklist

• Changes tested locally
• Code reviewed
• Documentation updated (if necessary)
• Unit tests added (if applicable)

Additional Notes

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[danielaskdd]

It appears the drop function in BaseGraphStorage has not been implemented yet. Additionally, the abstract method in BaseGraphStorage has been updated. Please sync with the main branch to incorporate the latest changes.

For verification, kindly conduct a thorough test of all graph-related functionalities in the WebUI of LightRAG Server, including:

• Graph Retrieval: Ensure the max depth and max nodes options are functioning as intended.
• Node Expand: Validate the expand feature works correctly.
• Clear Document: Ensure the clear document can remove all the data in Graph DB

To confirm successful implementation, please provide screenshots demonstrating all graph view functionalities are operating as expected.

Let me know if you have any questions or need further clarification.

[guzhu271]

[shell-nlp]

Great job, please merge this PR as soon as possible

[poppycoderr]

any update?

[danielaskdd]

Thank you for your congratulations and efforts. As LightRAG evolves, each storage implementation necessitates corresponding upgrades. Currently, we lack the resources to consistently track and maintain the advancements and performance optimizations for every storage type. To avoid impeding the overall progress of the LightRAG system, LightRAG will temporarily discontinue the integration of new storage implementations.

[github-actions]

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