Fix: Enable Kuzu Concurrency

[amritpal-singh-98]

Description

Currently, creating multiple [Async]Memory instances pointing to the same Kuzu DB file will raise an error (Could not set lock on file : /path/to/database/example.kuzu). This is due to limitations in the way that Kuzu handles file locking and concurrency - see Connections and Concurrency | Kuzu. Specifically, in order to use the same Kuzu DB file, connections need to use the same kuzu.Database object. This PR ensures that kuzu.Database objects are reused when attempting to connect to the same .kuzu DB file.

This allows multiple [Async]Memory instances to point to the same Kuzu DB file without error and function as expected. (This is often the case in Jupyter notebooks and async code, for example.

Type of change

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• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Small change - tested accessing the same Kuzu DB file from two separate mem0 Memory and AsyncMemory instances and validated that read/write operations to the same underlying Kuzu DB file works as expected. Previously an error related to file locking was raised when attempting to create the second mem0 [Async]Memory instance pointing to the same Kuzu DB.

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• Test Script - test_script.py

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed

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