@GwtCompatible
@ElementTypesAreNonnullByDefault
final class NullnessCasts {
  /**
   * Accepts a {@code @Nullable T} and returns a plain {@code T}, without performing any check that
   * that conversion is safe.
   *
   * <p>This method is intended to help with usages of type parameters that have {@linkplain
   * ParametricNullness parametric nullness}. If a type parameter instead ranges over only non-null

    return (format == this) ? str : convert(format, str);
  }

  /** Enum values can override for performance reasons. */
  String convert(CaseFormat format, String s) {
    // deal with camel conversion
    StringBuilder out = null;
    int i = 0;
    int j = -1;
    while ((j = wordBoundary.indexIn(s, ++j)) != -1) {
      if (i == 0) {
        // include some extra space for separators

    * <abbr title="en anglais : forms">les formulaires</abbr>.
    * <abbr title="en anglais : files">les fichiers</abbr>.
* <abbr title="aussi connu sous le nom de : serialization, parsing, marshalling">La conversion</abbr> des données de sortie : conversion des données et types Python en données réseau (au format <abbr title="JavaScript Object Notation">JSON</abbr>), permettant de convertir :
    * les types Python (`str`, `int`, `float`, `bool`, `list`, etc).

El `Union` en `Union[str, None]` no es usado por FastAPI (FastAPI solo usará la parte `str`), pero el `Union[str, None]` le permitirá a tu editor ayudarte a encontrar errores en tu código.

///

## Conversión de tipos de parámetros de query

También puedes declarar tipos `bool` y serán convertidos:

```Python hl_lines="9"
{!../../docs_src/query_params/tutorial003.py!}
```

En este caso, si vas a:

```

	FMULS	F1, F0, F2				// 53011010
	FDIVS	F1, F0, F2				// 53011018
	FMINS	F1, F0, F2				// 53011028
	FMAXS	F1, F0, F2				// 53111028
	FSQRTS	F0, F1					// d3000058

	// 20.7: Single-Precision Floating-Point Conversion and Move Instructions
	FCVTWS	F0, X5					// d31200c0
	FCVTWS.RNE	F0, X5				// d30200c0
	FCVTWS.RTZ	F0, X5				// d31200c0
	FCVTWS.RDN	F0, X5				// d32200c0
	FCVTWS.RUP	F0, X5				// d33200c0

)

// FuncName - SQL function name.
type FuncName string

// SQL Function name constants
const (
	// Conditionals
	sqlFnCoalesce FuncName = "COALESCE"
	sqlFnNullIf   FuncName = "NULLIF"

	// Conversion
	sqlFnCast FuncName = "CAST"

	// Date and time
	sqlFnDateAdd     FuncName = "DATE_ADD"
	sqlFnDateDiff    FuncName = "DATE_DIFF"
	sqlFnExtract     FuncName = "EXTRACT"
	sqlFnToString    FuncName = "TO_STRING"

That means that **any value** read in Python from an environment variable **will be a `str`**, and any conversion to a different type or any validation has to be done in code.

/// check

Also notice that **FastAPI** is smart enough to notice that the path parameter `item_id` is a path parameter and `q` is not, so, it's a query parameter.

///

## Query parameter type conversion

You can also declare `bool` types, and they will be converted:

//// tab | Python 3.10+

```Python hl_lines="7"
{!> ../../docs_src/query_params/tutorial003_py310.py!}
```

////

}
```

/// note

Notice that even though the `item` was declared the same way as before, it is now expected to be inside of the body with a key `item`.

///

**FastAPI** will do the automatic conversion from the request, so that the parameter `item` receives its specific content and the same for `user`.

It will perform the validation of the compound data, and will document it like that for the OpenAPI schema and automatic docs.

/// check

Dadurch erhalten Sie Editor-Unterstützung innerhalb Ihrer Funktion, mit Fehlerprüfungen, Codevervollständigung, usw.

///

## Daten-<abbr title="Auch bekannt als: Serialisierung, Parsen, Marshalling">Konversion</abbr>

Wenn Sie dieses Beispiel ausführen und Ihren Browser unter <a href="http://127.0.0.1:8000/items/3" class="external-link" target="_blank">http://127.0.0.1:8000/items/3</a> öffnen, sehen Sie als Response:

```JSON