Function function_signature_to_arrow_schemas 

pub fn function_signature_to_arrow_schemas(
    signature: &str,
    large_int_as_binary: bool,
) -> Result<(Schema, Schema)>

Returns the Arrow schemas for a function’s inputs and outputs as (input_schema, output_schema).

large_int_as_binary must match the value passed to decode_call_inputs / decode_call_outputs for the resulting batch to match this schema.