*
   * @throws IllegalArgumentException if the stream consists of two or more elements.
   * @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.
   */
  @SuppressWarnings("unchecked")

def lang_callback(lang: Optional[str]) -> Union[str, None]:
    if lang is None:
        return None
    lang = lang.lower()
    return lang


def complete_existing_lang(incomplete: str):
    lang_path: Path
    for lang_path in get_lang_paths():
        if lang_path.is_dir() and lang_path.name.startswith(incomplete):
            yield lang_path.name


@app.callback()
def callback() -> None:
    if is_mkdocs_insiders():

			if tc.error == "" && err != nil {
				t.Fatalf("expected no error, got %v", err)
			}
			if tc.error != "" {
				if err == nil {
					t.Fatalf("expected error to include \"%s\" but got none", tc.error)
				}
				if !strings.Contains(err.Error(), tc.error) {
					t.Fatalf("expected \"%s\" in error, got %v", tc.error, err)
				}
			}

			commandOutput := out.String()

The way to describe this in OpenAPI, is to mark that field as **required**, because it will always be there.

Because of that, the JSON Schema for a model can be different depending on if it's used for **input or output**:

* for **input** the `description` will **not be required**
* for **output** it will be **required** (and possibly `None`, or in JSON terms, `null`)

    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:

    }

    public Collection<DefaultType> types() {
        return Arrays.asList(
                // Maven types
                new DefaultType(Type.POM, Language.NONE, "pom", null, false),
                new DefaultType(Type.BOM, Language.NONE, "pom", null, false),
                new DefaultType(Type.MAVEN_PLUGIN, Language.JAVA_FAMILY, "jar", null, false, JavaPathType.CLASSES),
                // Java types

				t.Errorf("#%d: %q: expected error %q; got none", i, test.input, test.error)
			}
			continue
		}
		if !strings.Contains(err.Error(), test.error) {
			t.Errorf("#%d: expected error %q; got %q", i, test.error, err)
			continue
		}
	}
}

func runBadTest(i int, test badExprTest, t *testing.T) (err error) {
	p := NewParser(nil, nil, nil) // Expression evaluation uses none of these fields of the parser.

@app.get("/query_examples/")
def query_examples(
    data: Union[str, None] = Query(
        default=None,
        examples=[
            "json_schema_query1",
            "json_schema_query2",
        ],
        openapi_examples={
            "Query One": {
                "summary": "Query One Summary",
                "description": "Query One Description",
                "value": "query1",
            },

/// tip | Dica

Fazer com que o modelo de retorno garanta que um valor esteja sempre disponível e sempre seja um `int` (não `None`) é muito útil para os clientes da API, eles podem escrever código muito mais simples com essa certeza.

    @Override
    public void run() {}
  }
  // The thread executing the task publishes itself to the superclass' reference and the thread
  // interrupting sets DONE when it has finished interrupting.
  private static final Runnable DONE = new DoNothingRunnable();
  private static final Runnable PARKED = new DoNothingRunnable();
  // Why 1000?  WHY NOT!
  private static final int MAX_BUSY_WAIT_SPINS = 1000;

  @Override