Plugin Devtool Prompt for ChatGPT explained

I am using the ChatGPT devtool to check the “Prompt for ChatGPT” for the starter Todo List plugin GitHub - openai/plugins-quickstart: Get a ChatGPT plugin up and running in under 5 minutes!. I am seeing the following:

I don’t understand the coding syntax. For example:

// Get the list of todos
type getTodos = (_: {
// The name of the user.
username: string,
}) => any;

I have never seen for example (_: { //something }) => any;

What is this prompt?

I think your yaml description gets compiled into this intermediate representation.

Interestingly, even though the yaml describes some of the IO format, that transpiled output seems to use “any” a lot for things I’d expect to be labelled as structured data.