# OpenAPI Callbacks { #openapi-callbacks }

You could create an API with a *path operation* that could trigger a request to an *external API* created by someone else (probably the same developer that would be *using* your API).

If you use a `requirements.txt` file you could specify the version with:

```txt
fastapi[standard]==0.112.0
```

that would mean that you would use exactly the version `0.112.0`.

Or you could also pin it with:

```txt
fastapi[standard]>=0.112.0,<0.113.0
```

Here's an example of how an HTTPS API could look like, step by step, paying attention mainly to the ideas important for developers.

### Domain Name { #domain-name }

It would probably all start by you **acquiring** some **domain name**. Then, you would configure it in a DNS server (possibly your same cloud provider).

# OpenAPI Webhooks { #openapi-webhooks }

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

But for the generated client, we could **modify** the OpenAPI operation IDs right before generating the clients, just to make those method names nicer and **cleaner**.

We could download the OpenAPI JSON to a file `openapi.json` and then we could **remove that prefixed tag** with a script like this:

{* ../../docs_src/generate_clients/tutorial004.py *}

		u, ok, err := globalIAMSys.CheckKey(r.Context(), accessKey)
		if err != nil {
			return auth.Credentials{}, false, ErrIAMNotInitialized
		}
		if !ok {
			// Credentials could be valid but disabled - return a different
			// error in such a scenario.
			if u.Credentials.Status == auth.AccountOff {
				return cred, false, ErrAccessKeyDisabled
			}
			return cred, false, ErrInvalidAccessKeyID

Downloading and installing the package dependencies **could take minutes**, but using the **cache** would **take seconds** at most.

And as you would be building the container image again and again during development to check that your code changes are working, there's a lot of accumulated time this would save.

This Manager Process would probably be the one listening on the **port** in the IP. And it would transmit all the communication to the worker processes.

Those worker processes would be the ones running your application, they would perform the main computations to receive a **request** and return a **response**, and they would load anything you put in variables in RAM.

The **default** value of the **function parameter** is the **actual default** value, that's more intuitive with Python in general. 😌

 *       suite()} method with {@code Suppress}. Would {@code FooTest} itself be suppressed, too?
 *   <li>In at least one case, a use of {@code sun.misc.FpUtils}, the test will not even
 *       <i>compile</i> against Android. Now, this might be an artifact of our build system, one
 *       that we could probably work around. Or we could manually strip the test from open-source