Então se você tiver um objeto `alguma_coisa` (que pode *não* ser uma função) que você possa "chamar" (executá-lo) dessa maneira:

```Python
something()
```

ou

```Python
something(some_argument, some_keyword_argument="foo")
```

Então esse objeto é um "chamável".

## Classes como dependências

   * String.class}, then {@code new TypeResolver().where(formal, actual)} will {@linkplain
   * #resolveType resolve} {@code ParameterizedType List<T>} to {@code List<String>}, and resolve
   * {@code Map<T, Something>} to {@code Map<String, Something>} etc. Similarly, {@code formal} and
   * {@code actual} can be {@code Map<K, V>} and {@code Map<String, Integer>} respectively, or they

`Optional[Something]` é na verdade um atalho para `Union[Something, None]`, eles são equivalentes.

Isso também significa que no Python 3.10, você pode utilizar `Something | None`:

//// tab | Python 3.10+

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

////

`Optional[Something]` là một cách viết ngắn gọn của `Union[Something, None]`, chúng là tương đương nhau.

Điều này cũng có nghĩa là trong Python 3.10, bạn có thể sử dụng `Something | None`:

//// tab | Python 3.10+

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

   * someone still manages to pass null, let's continue to have the method work.
   *
   * (PatternFilenameFilter is of course one of those classes that shouldn't be a publicly visible
   * class to begin with but rather something returned from a static factory method whose declared
   * return type is plain FilenameFilter. If we made such a change, then the annotation we choose

   *
   * <pre>{@code
   * public void useStreamNicely() throws IOException {
   *   SomeStream stream = new SomeStream("foo");
   *   boolean threw = true;
   *   try {
   *     // ... code which does something with the stream ...
   *     threw = false;
   *   } finally {
   *     // If an exception occurs, rethrow it only if threw==false:
   *     Closeables.close(stream, threw);
   *   }
   * }
   * }</pre>
   *

   * useful to call from vanilla JavaScript because it returns an instance of Class, which can't be
   * converted to a standard JavaScript type. (Contrast to something like String or boolean.) Since
   * we're not calling it from JavaScript, we suppress the warning.
   */
  @JsMethod
  @SuppressWarnings("unusable-by-js")

/// tip

The actual callback is just an HTTP request.

When implementing the callback yourself, you could use something like <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a> or <a href="https://requests.readthedocs.io/" class="external-link" target="_blank">Requests</a>.

///

    // Read a token68, a sequence of parameters, or nothing.
    val commaPrefixed = skipCommasAndWhitespace()
    peek = readToken()
    if (peek == null) {
      if (!exhausted()) return // Expected a token; got something else.
      result.add(Challenge(schemeName, emptyMap()))
      return
    }

    var eqCount = skipAll('='.code.toByte())
    val commaSuffixed = skipCommasAndWhitespace()

  private static final class TestTable<R, C, V> implements Table<R, C, V>, Serializable {
    final Table<R, C, V> delegate = HashBasedTable.create();
    public final Object mutex = new Object[0]; // something Serializable

    @Override
    public String toString() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.toString();
    }

    @Override
    public boolean equals(@Nullable Object o) {