Reformat and improve RAG module and agents

[ZiTao-Li]

Description

Updates

Changes on code structure

• migrate and reformat RAG/knowledge module(s) and RAG agent(s) from examples to a module in src
• add llama-index as rag_requires in setup.py

Changes on the RAG agent module

• be compatible with the new KnowledgeBank feature
• the configurations for the RAG-related functionalities are relocated back to knowledge modules
• the retrieve method merges the retrievers from the KnowledgeBank members

Changes on the RAG/knowledge module

• Rename the RAG modules to Knowledge (e.g., LlamaIndexRAG -> LlamaIndexKnowledge)
• store and persist processed embeddings/indices/documents
• support loading multiple doc types and dirs for one index
• support docs management in the obtained (persisted) index
• add a refresh function to update the index when needed
• enable agents to reset or add new retrievers

Improving utility of knowledge module

• reformat easy-to-use knowledge module config: the new format only configure the KnowledgeBank
• introduce KnowledgeBank:
  • KnowledgeBank provides an easier way to initialize a knowledge object, just call add_data_as_knowledge with knowledge_id (a string as the identifier for this knowledge object), emb_model_name (the name of the embedding model config) and data_dirs_and_types (a dictionary of data directories and the wanted file extensions). As shown in the rag_example.py

     knowledge_bank.add_data_as_knowledge(
        knowledge_id="agentscope_tutorial_rag",
        emb_model_name="qwen_emb_config",
        data_dirs_and_types={
            "../../docs/sphinx_doc/en/source/tutorial": [".md"],
        },
    )
    

  • Knowledge objects in KnowledgeBank can be shared and duplicated by multiple agents, which can avoid embedding duplicated documents.
  • RAG agents can load multiple Knowledge objects (based on the "knowledge_id" in knowledge_config.json) with associated retrievers to perform multi-source information retrieval. Just need to pass the agent into KnowledgeBank.equip function.

Toturial

Both English and Chinese tutorial are added as 209-rag.md .

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Checklist

Please check the following items before code is ready to be reviewed.

• [x] Code has passed all tests
• [x] Docstrings have been added/updated in Google Style
• [x] Documentation has been updated
• [x] Code is ready for review

[DavdGao]

@ZiTao-Li Is this PR ready for review?

[DavdGao]

The ImportError of LlamaIndex library is still exposed to users who don't use RAG module.