`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

</div>

/// note

The command `uvicorn main:app` refers to:

* `main`: the file `main.py` (the Python "module").
* `app`: the object created inside of `main.py` with the line `app = FastAPI()`.

It is equivalent to:

```Python
from main import app
```

///

Each alternative ASGI server program would have a similar command, you can read more in their respective documentation.

/// warning

Dans l'exemple ci-dessus, ils ont des valeurs par défaut qui sont `skip=0` et `limit=10`.

Donc, accéder à l'URL :

```
http://127.0.0.1:8000/items/
```

serait équivalent à accéder à l'URL :

```
http://127.0.0.1:8000/items/?skip=0&limit=10
```

Mais si vous accédez à, par exemple :

```
http://127.0.0.1:8000/items/?skip=20
```

    /**
     * Calculates the effective repositories for the given input repositories which are assumed to be already mirrored
     * (if applicable). This process will essentially remove duplicate repositories by merging them into one equivalent
     * repository. It is worth to point out that merging does not simply choose one of the input repositories and
     * discards the others but actually combines their possibly different policies.
     *

   * evaluate the integral of the function from 7.0 to 10.0.
   *
   * Using integrals guarantees that the effect of a single acquire(3) is equivalent to {
   * acquire(1); acquire(1); acquire(1); }, or { acquire(2); acquire(1); }, etc, since the integral
   * of the function in [7.0, 10.0] is equivalent to the sum of the integrals of [7.0, 8.0], [8.0,
   * 9.0], [9.0, 10.0] (and so on), no matter what the function is. This guarantees that we handle

  RangeMap<K, V> subRangeMap(Range<K> range);

  /**
   * Returns {@code true} if {@code obj} is another {@code RangeMap} that has an equivalent {@link
   * #asMapOfRanges()}.
   */
  @Override
  boolean equals(@Nullable Object o);

  /** Returns {@code asMapOfRanges().hashCode()}. */
  @Override
  int hashCode();

   * note that the execution order of all listeners is ultimately chosen by the implementations of
   * the supplied executors.
   *
   * <p>This method is idempotent. Calling it several times in parallel is semantically equivalent
   * to calling it exactly once.
   *
   * @since 10.0 (present in 1.0 as {@code run})
   */
  public void execute() {
    // Lock while we update our state so the add method above will finish adding any listeners

   */
  public abstract ContiguousSet<C> intersection(ContiguousSet<C> other);

  /**
   * Returns a range, closed on both ends, whose endpoints are the minimum and maximum values
   * contained in this set. This is equivalent to {@code range(CLOSED, CLOSED)}.
   *
   * @throws NoSuchElementException if this set is empty
   */
  public abstract Range<C> range();

  /**

	defer removeRoots(disks)

	// uses *testing.B and the object Layer to run the benchmark.
	runPutObjectBenchmarkParallel(b, objLayer, objSize)
}

// randomly picks a character and returns its equivalent byte array.
func getRandomByte() []byte {
	const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
	// seeding the random number generator.
	rand.Seed(UTCNow().UnixNano())

#### Sobre `**user_dict` { #about-user-dict }

`UserInDB(**user_dict)` significa:

*Pasa las claves y valores de `user_dict` directamente como argumentos clave-valor, equivalente a:*

```Python
UserInDB(
    username = user_dict["username"],
    email = user_dict["email"],
    full_name = user_dict["full_name"],
    disabled = user_dict["disabled"],