Support for more Schema types like "anyOf"

[icnahom]

What feature would you like to see?

I would like to see some missing but important schema types like anyOf .

Here are all the schema types for reference: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/control-generated-output#fields

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.