Support python `Literal` types when defining JSON or FunctionCalling schemas.

Description of the feature request:

String literal types should create Enums in the generated schema.

What problem are you trying to solve with this feature?

No response

Any other information you'd like to share?

No response

@MarkDaoust you mention "generated" - is there a private method that generates protos.Schema somewhere ?

I was about to write a feature request for a from_object() like in node.js to convert a pydantic object to Schema.

Hi @yan-hic,

The code is here:

generative-ai-python/google/generativeai/types/content_types.py

Lines 337 to 342 in 8f77cc6

    
           def _schema_for_class(cls: TypedDict) -> dict[str, Any]: 
        
               schema = _build_schema("dummy", {"dummy": (cls, pydantic.Field())}) 
        
               return schema["properties"]["dummy"] 
        
           def _schema_for_function(

It uses pydantic to do the conversion already, but I haven't tested actually passing pydantic objects.
Similarly, I haven't tried this with types like Literal['a', 'b'].

	def _schema_for_class(cls: TypedDict) -> dict[str, Any]:
	schema = _build_schema("dummy", {"dummy": (cls, pydantic.Field())})
	return schema["properties"]["dummy"]


	def _schema_for_function(