{* ../../docs_src/query_params_str_validations/tutorial004.py hl[10] *}

Cette expression régulière vérifie que la valeur passée comme paramètre :

* `^` : commence avec les caractères qui suivent, avec aucun caractère avant ceux-là.

`Header` tem algumas funcionalidades a mais em relação a `Path`, `Query` e `Cookie`.

A maioria dos cabeçalhos padrão são separados pelo caractere "hífen", também conhecido como "sinal de menos" (`-`).

Mas uma variável como `user-agent` é inválida em Python.

Portanto, por padrão, `Header` converterá os caracteres de nomes de parâmetros de sublinhado (`_`) para hífen (`-`) para extrair e documentar os cabeçalhos.

    executeSynchronously(Request(server.url("/")))
    assertThat(server.takeRequest().exchangeIndex).isEqualTo(0)
    assertThat(server.takeRequest().exchangeIndex).isEqualTo(1)
  }

  /** We forbid non-ASCII characters in outgoing request headers, but accept UTF-8.  */
  @Test
  fun responseHeaderParsingIsLenient() {
    val headersBuilder = Headers.Builder()
    headersBuilder.add("Content-Length", "0")

- kubeadm: fixed a bug in the underlying library for diff related to characters like '%' ([#73941](https://github.com/kubernetes/kubernetes/pull/73941), [@neolit123](https://github.com/neolit123))

La mayoría de los headers estándar están separados por un carácter "guion", también conocido como el "símbolo menos" (`-`).

Pero una variable como `user-agent` es inválida en Python.

Así que, por defecto, `Header` convertirá los caracteres de los nombres de los parámetros de guion bajo (`_`) a guion (`-`) para extraer y documentar los headers.

      new SparseImmutableTable<>(CELLS.asList(), ROW_SPACE, COLUMN_SPACE);

  private static final DenseImmutableTable<Character, Integer, String> DENSE =
      new DenseImmutableTable<>(CELLS.asList(), ROW_SPACE, COLUMN_SPACE);

  @Override
  Iterable<ImmutableTable<Character, Integer, String>> getTestInstances() {

    abstract Table<String, Integer, Character> createTable();

    @Override
    @SuppressWarnings("unchecked")
    public Cell<String, Integer, Character>[] createArray(int length) {
      return (Cell<String, Integer, Character>[]) new Cell<?, ?, ?>[length];
    }

    @Override
    public List<Cell<String, Integer, Character>> order(
        List<Cell<String, Integer, Character>> insertionOrder) {

    Table<Integer, String, Character> original = HashBasedTable.create();
    Table<String, Integer, Character> transpose = transpose(original);
    transpose.put("foo", 1, 'a');
    assertEquals((Character) 'a', original.get(1, "foo"));
  }

  public void testTransposedViews() {
    Table<Integer, String, Character> original = HashBasedTable.create();
    Table<String, Integer, Character> transpose = transpose(original);

  @SuppressWarnings("unchecked") // C can only be @Nullable Character or Character
  protected @NonNull C cellValue(Character character) {
    return (C) character;
  }

  // Only safe wrt. ClassCastException. Not null-safe (can be used to test expected Table NPEs)
  @SuppressWarnings("unchecked")
  protected C nullableCellValue(@Nullable Character character) {
    return (C) character;
  }

    int i = 0;
    for (Object e : elements) {
      array[i++] = (Character) e;
    }
    return create(array);
  }

  /**
   * Creates a new collection containing the given elements; implement this method instead of {@link
   * #create(Object...)}.
   */
  protected abstract List<Character> create(Character[] elements);

  @Override
  public Character[] createArray(int length) {