LangChain Community Removal

[alexthomas93]

This PR removes the LangChain Community package dependency. It ports the remaining small utility classes and helper functions directly into the LangChain Neo4j codebase, reducing external dependencies while maintaining full existing functionality. The classes and functions ported are:

from langchain_community.chains.graph_qa.prompts import (
    CYPHER_GENERATION_PROMPT,
    CYPHER_QA_PROMPT,
)
from langchain_community.graphs.graph_document import GraphDocument, Node, Relationship
from langchain_community.graphs.graph_store import GraphStore
from langchain_community.vectorstores.utils import DistanceStrategy

This PR also replaces an import of the maximal_marginal_relevance function from LangChain Community with one from LangChain Core.

[alexthomas93]

@CodiumAI-Agent /update_changelog

[CodiumAI-Agent]

Changelog updates: 🔄

2024-11-20

Changed

• Removed dependency on LangChain Community package by integrating necessary components directly into the LangChain Neo4j codebase.
• Updated imports to use LangChain Core and LangChain Neo4j modules.

to commit the new content to the CHANGELOG.md file, please type:
'/update_changelog --pr_update_changelog.push_changelog_changes=true'