I think `Union[SomeType, None]` is more explicit about what it means.

It's just about the words and names. But those words can affect how you and your teammates think about the code.

As an example, let's take this function:

{* ../../docs_src/python_types/tutorial009c.py hl[1,4] *}

blank_issues_enabled: false
contact_links:
  - name: MinIO Community Support
    url: https://slack.min.io
    about: Join here for Community Support
  - name: MinIO SUBNET Support
    url: https://min.io/pricing

wandered about in the wood, `is to grow to my right size again;
and the second thing is to find my way into that lovely garden.
I think that will be the best plan.'

  It sounded an excellent plan, no doubt, and very neatly and
simply arranged; the only difficulty was, that she had not the
smallest idea how to set about it; and while she was peering
about anxiously among the trees, a little sharp bark just over

 * thrown or a simple string message. In addition, a problem carries a hint about its source.
 *
 * @since 4.0.0
 */
@Experimental
@Immutable
public interface BuilderProblem {

    /**
     * Gets the hint about the source of the problem. While the syntax of this hint is unspecified and depends on the

```

</div>

////

This information will be useful when learning about [Virtual Environments](virtual-environments.md){.internal-link target=_blank}.

## Conclusion { #conclusion }

With this you should have a basic understanding of what **environment variables** are and how to use them in Python.

/// note

Some response codes (see the next section) indicate that the response does not have a body.

FastAPI knows this, and will produce OpenAPI docs that state there is no response body.

///

## About HTTP status codes { #about-http-status-codes }

/// note

If you already know what HTTP status codes are, skip to the next section.

///

In HTTP, you send a numeric status code of 3 digits as part of the response.

///

/// tip

To declare form bodies, you need to use `Form` explicitly, because without it the parameters would be interpreted as query parameters or body (JSON) parameters.

///

## About "Form Fields" { #about-form-fields }

The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.

I'll show you some concrete examples in the next chapters.

---

Then the next concepts to consider are all about the program running your actual API (e.g. Uvicorn).

## Program and Process { #program-and-process }

We will talk a lot about the running "**process**", so it's useful to have clarity about what it means, and what's the difference with the word "**program**".

### What is a Program { #what-is-a-program }

     */
    InputStream getInputStream() throws IOException;

    /**
     * Provides a user-friendly hint about the location of the source. This could be a local file path, a URI or just an
     * empty string. The intention is to assist users during error reporting.
     *
     * @return A user-friendly hint about the location of the source, never {@code null}.
     */
    String getLocation();

package org.apache.maven.building;

/**
 * Describes a problem that was encountered during settings building. A problem can either be an exception that was
 * thrown or a simple string message. In addition, a problem carries a hint about its source, e.g. the settings file
 * that exhibits the problem.
 *
 * @deprecated since 4.0.0, use {@link org.apache.maven.api.services} instead
 */
@Deprecated(since = "4.0.0")
public interface Problem {

    /**