[UNIT] New unit on a Agentic RAG use case (Unit 3)

[burtenshaw]

This PR add Unit 3 on an Agentic RAG use case:

It builds opon these PRs:

• @sergiopaniego [UNIT] Use case Agentic RAG with smolagents - release 25/03 #297
• @davidberenstein1957 [UNIT] Use case Agentic RAG with LlamaIndex - release TBD #232

Remaining work on this PR

• review material, code, and copy
• define student's approach to use case. i.e. should the build the agent in a space
• add frame works tabs for LlamaIndex and LangGraph

[sergiopaniego]

I've created a PR with some suggestions 😄

A few points that also need to be addressed:

• In invitees.mdx, a unit3-invitees dataset is mentioned, but it isn't available yet. Has it already been created?
• There are mentions of Python files throughout the text (e.g., retriever.py and tools.py). I find this a bit confusing. Perhaps adding a file structure overview would help clarify things.
• Directly related to the previous point, no notebooks/Colab files are included in the PR.

I can work on any of these. Just leaving the points here to avoid duplicating work 😄

[burtenshaw]

Thanks @sergiopaniego. I merged your PR. Replying in line:

In invitees.mdx, a unit3-invitees dataset is mentioned, but it isn't available yet. Has it already been created?

No, we need to create this dataset.

There are mentions of Python files throughout the text (e.g., retriever.py and tools.py). I find this a bit confusing. Perhaps adding a file structure overview would help clarify things.

The idea was that students use a template repo with empty files in that they need to complete to make the use case work. This could be a space.

Directly related to the previous point, no notebooks/Colab files are included in the PR.

No notebooks here. The idea was that students make an application, but you're right it's not clear from the current material.

[sergiopaniego]

Thanks for the details @burtenshaw

I've generated #340 for the LlamaIndex tab.

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