Support for context caching

[haroldsnyers]

Context caching does not seem to be support with Langchain.

With the new library, one can easily add parts to the cache as such

system_instruction = """
You are an expert researcher who has years of experience in conducting systematic literature surveys and meta-analyses of different topics.
You pride yourself on incredible accuracy and attention to detail. You always stick to the facts in the sources provided, and never make up new facts.
Now look at the research paper below, and answer the following questions in 1-2 sentences.
"""

cached_content = client.caches.create(
    model=MODEL_ID,
    config=CreateCachedContentConfig(
        contents=[
            Content(
                role="user",
                parts=[
                    Part.from_uri(
                        file_uri="gs://cloud-samples-data/generative-ai/pdf/2312.11805v3.pdf",
                        mime_type="application/pdf",
                    ),
                    Part.from_uri(
                        file_uri="gs://cloud-samples-data/generative-ai/pdf/2403.05530.pdf",
                        mime_type="application/pdf",
                    ),
                ],
            )
        ],
        system_instruction=system_instruction,
        ttl="3600s",
    ),
)

[lkuligin]

would you like to work on the PR?