I tested several ideas in the most popular Python editors: PyCharm, VS Code, Jedi based editors.

By the last [Python Developer Survey](https://www.jetbrains.com/research/python-developers-survey-2018/#development-tools), that covers about 80% of the users.

With this, we get tooling support, from editors and mypy as this code is correct in terms of types, but we also get the data filtering from FastAPI.

How does this work? Let's check that out. 🤓

### Type Annotations and Tooling { #type-annotations-and-tooling }

First let's see how editors, mypy and other tools would see this.

# EditorConfig helps developers define and maintain consistent
# coding styles between different editors and IDEs
# editorconfig.org

root = true

[*]

indent_style = space
indent_size = 4

end_of_line = lf
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true

spelling_languages = en-US

# Markdown files sometimes need trailing whitespaces.
[*.md]
trim_trailing_whitespace = false

There were even some changes to Pydantic itself to support this.

The previous screenshots were taken with [Visual Studio Code](https://code.visualstudio.com).

But you would get the same editor support with [PyCharm](https://www.jetbrains.com/pycharm/) and most of the other Python editors:

<img src="/img/tutorial/body/image05.png">

/// tip

 *
 * <p>Strategies work with domtrip Documents for perfect formatting preservation.
 * Individual strategies can create domtrip Editors from Documents as needed:
 * <pre>
 * Editor editor = new Editor(document);
 * // ... perform domtrip operations ...
 * // Document is automatically updated
 * </pre>
 */
public interface UpgradeStrategy {

    /**

### Application Discovery { #application-discovery }

/// tip

Some editors check for unused function parameters, and show them as errors.

Using these `dependencies` in the *path operation decorator* you can make sure they are executed while avoiding editor/tooling errors.

By doing that, your editor can provide support even while processing items from the list:

<img src="/img/python-types/image05.png">

Without types, that's almost impossible to achieve.

Notice that the variable `item` is one of the elements in the list `items`.

And still, the editor knows it is a `str`, and provides support for that.

 *
 * <p>This class recursively discovers all POM files in a Maven project hierarchy
 * and loads them as domtrip Documents. Individual strategies can create domtrip Editors
 * from these Documents as needed for superior formatting preservation.
 */
public class PomDiscovery {

    private PomDiscovery() {
        // noop
    }

    /**

 * and reduces code duplication across strategy implementations.
 *
 * <p>Strategies work with domtrip Documents for perfect formatting preservation.
 * Subclasses can create domtrip Editors from Documents as needed:
 * <pre>
 * Editor editor = new Editor(document);
 * // ... perform domtrip operations ...
 * // Document is automatically updated
 * </pre>
 */
public abstract class AbstractUpgradeStrategy implements UpgradeStrategy {