///

## Types and validation { #types-and-validation }

These environment variables can only handle text strings, as they are external to Python and have to be compatible with other programs and the rest of the system (and even with different operating systems, as Linux, Windows, macOS).

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

For many scenarios, you can handle security (authorization, authentication, etc.) with dependencies, using `Depends()`.

But when you want to also declare OAuth2 scopes, you can use `Security()` instead of `Depends()`.

[`MultiHandler`](/pkg/log/slog#MultiHandler) that invokes all the given Handlers.
Its `Enable` method reports whether any of the handlers' `Enabled` methods
return true.
Its `Handle`, `WithAttr` and `WithGroup` methods call the corresponding method

pkg log/slog, func NewMultiHandler(...Handler) *MultiHandler #65954
pkg log/slog, method (*MultiHandler) Enabled(context.Context, Level) bool #65954
pkg log/slog, method (*MultiHandler) Handle(context.Context, Record) error #65954
pkg log/slog, method (*MultiHandler) WithAttrs([]Attr) Handler #65954
pkg log/slog, method (*MultiHandler) WithGroup(string) Handler #65954

pkg syscall (windows-386), const TH32CS_SNAPTHREAD ideal-int
pkg syscall (windows-386), func CreateToolhelp32Snapshot(uint32, uint32) (Handle, error)
pkg syscall (windows-386), func Process32First(Handle, *ProcessEntry32) error
pkg syscall (windows-386), func Process32Next(Handle, *ProcessEntry32) error
pkg syscall (windows-386), type ProcessEntry32 struct
pkg syscall (windows-386), type ProcessEntry32 struct, DefaultHeapID uintptr

			return errFileAccessDenied
		case isSysErrPathNotFound(err):
			// This is a special case should be handled only for
			// windows, because windows API does not return "not a
			// directory" error message. Handle this specifically
			// here.
			return errFileAccessDenied
		}
	}
	return err
}

// Reliably retries os.RemoveAll if for some reason os.RemoveAll returns
// syscall.ENOTEMPTY (children has files).

 * This exception indicates a failure or error that occurred while extracting content from a crawled resource.
 * It extends {@link org.codelibs.fess.crawler.exception.CrawlerSystemException} and provides constructors
 * to handle different scenarios such as wrapping another exception or providing a specific error message.
 */
public class ExtractException extends CrawlerSystemException {

    private static final long serialVersionUID = 1L;

## Use Case { #use-case }

Let's start with an example **use case** and then see how to solve it with this.

Let's imagine that you have some **machine learning models** that you want to use to handle requests. 🤖

The same models are shared among requests, so, it's not one model per request, or one per user or something similar.

* text eol=lf

#
# The above will handle all files NOT found below
# https://help.github.com/articles/dealing-with-line-endings/
# https://github.com/Danimoth/gitattributes

# These are explicitly windows files and should use crlf
*.bat           text eol=crlf

# These files are text and should be normalized (Convert crlf => lf)
*.bash          text eol=lf
*.css           text diff=css
*.htm           text diff=html

Create a function to be run as the background task.

It is just a standard function that can receive parameters.

It can be an `async def` or normal `def` function, **FastAPI** will know how to handle it correctly.

In this case, the task function will write to a file (simulating sending an email).

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`: