Typing a StepsFunction directly seems to require a streamingCallback argument, despite type parameters?

[cabljac]

Hi, I was moving some code about and playing around with the types in the js packages, and trying to call a typed stepsFunction i get an error:

import z from "zod";

import { StepsFunction } from "@genkit-ai/flow";

const testInputSchema = z.string();
const testOutputSchema = z.string();

type TestStepsFunctionInput = StepsFunction<
  typeof testInputSchema,
  typeof testOutputSchema
>;

const testStepsFunction: TestStepsFunctionInput = async (input) => {
  return input;
};

testStepsFunction("test");

For example: