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## Expected Behavior
<!--- If you're describing a bug, tell us what should happen -->
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## Current Behavior
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If there's no `gzip` in the header, it will not try to decompress the body.

That way, the same route class can handle gzip compressed or uncompressed requests.

{* ../../docs_src/custom_request_and_route/tutorial001.py hl[8:15] *}

### Create a custom `GzipRoute` class { #create-a-custom-gziproute-class }

Next, we create a custom subclass of `fastapi.routing.APIRoute` that will make use of the `GzipRequest`.

## What is "Dependency Injection" { #what-is-dependency-injection }

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".

This way, you don't have to know beforehand what the valid field/attribute names are (as would be the case with Pydantic models).

This would be useful if you want to receive keys that you don't already know.

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Another useful case is when you want to have keys of another type (e.g., `int`).

That's what we are going to see here.

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#### What type of PR is this?

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#### What this PR does / why we need it:

This can be very useful for setting up **resources** that you need to use for the whole app, and that are **shared** among requests, and/or that you need to **clean up** afterwards. For example, a database connection pool, or loading a shared machine learning model.

## Use Case { #use-case }

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

Deploying a **FastAPI** application is relatively easy.

## What Does Deployment Mean { #what-does-deployment-mean }

To **deploy** an application means to perform the necessary steps to make it **available to the users**.

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### What is "Mounting" { #what-is-mounting }

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

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/// tip

Every time you install a **new package** in that environment, **activate** the environment again.

This makes sure that if you use a **terminal (<abbr title="command line interface">CLI</abbr>) program** installed by that package, you use the one from your virtual environment and not any other that could be installed globally, probably with a different version than what you need.

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