Let's imagine that loading the model can **take quite some time**, because it has to read a lot of **data from disk**. So you don't want to do it for every request.

Reading a file from disk is normally a costly (slow) operation, so you probably want to do it only once and then re-use the same settings object, instead of reading it for each request.

But every time we do:

```Python
Settings()
```

a new `Settings` object would be created, and at creation it would read the `.env` file again.

If the dependency function was just like:

```Python

OAuth2 foi projetado para que o backend ou a API pudesse ser independente do servidor que autentica o usuário.

Mas nesse caso, a mesma aplicação **FastAPI** irá lidar com a API e a autenticação.

Então, vamos rever de um ponto de vista simplificado:

* O usuário digita o `username` e a `senha` no frontend e aperta `Enter`.

    )

    @BeforeEach
    fun setUp() {
        val stepsCapturer = slot<BuildSteps.() -> Unit>()
        every { buildType.steps } returns steps
        every {
            buildType.steps(capture(stepsCapturer))
        } answers {
            stepsCapturer.captured(steps)
            mockk()
        }
    }

    @Test

) : RoutePlanner.Plan, ExchangeCodec.Carrier {
  /** True if this connect was canceled; typically because it lost a race. */
  @Volatile private var canceled = false

  // These properties are initialized by connect() and never reassigned.

  /** The low-level TCP socket. */
  private var rawSocket: Socket? = null

  /**
   * The application layer socket. Either an [SSLSocket] layered over [rawSocket], or [rawSocket]

    But this guide shows you, more or less, how they are intended to be used.

### Using Pydantic's `exclude_unset` parameter

If you want to receive partial updates, it's very useful to use the parameter `exclude_unset` in Pydantic's model's `.model_dump()`.

Like `item.model_dump(exclude_unset=True)`.

!!! info

There are many tools to generate clients from **OpenAPI**.

A common tool is <a href="https://openapi-generator.tech/" class="external-link" target="_blank">OpenAPI Generator</a>.

If you are building a **frontend**, a very interesting alternative is <a href="https://github.com/hey-api/openapi-ts" class="external-link" target="_blank">openapi-ts</a>.

## Client and SDK Generators - Sponsor

{!../../../docs_src/bigger_applications/app/main.py!}
```

and it will work correctly, together with all the other *path operations* added with `app.include_router()`.

!!! info "Very Technical Details"
    **Note**: this is a very technical detail that you probably can **just skip**.

    ---

    The `APIRouter`s are not "mounted", they are not isolated from the rest of the application.

# Please note that MKL on MacOS is still not supported.
# If you would like to use a local MKL instead of downloading, please set the
# environment variable "TF_MKL_ROOT" every time before build.
build:mkl --define=build_with_mkl=true --define=enable_mkl=true
build:mkl --define=tensorflow_mkldnn_contraction_kernel=0
build:mkl --define=build_with_openmp=true
build:mkl -c opt

    They are more relevant for older versions, before OpenAPI 3.1.0 was available.

    You can consider this a brief OpenAPI and JSON Schema **history lesson**. 🤓

!!! warning
    These are very technical details about the standards **JSON Schema** and **OpenAPI**.

    If the ideas above already work for you, that might be enough, and you probably don't need these details, feel free to skip them.