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

////

使用 `str | None` 而不是單純的 `str`，可以讓編輯器幫你偵測錯誤，例如你以為某個值一定是 `str`，但它其實也可能是 `None`。

### 類別作為型別 { #classes-as-types }

你也可以用類別來宣告變數的型別。

假設你有一個 `Person` 類別，帶有名稱：

{* ../../docs_src/python_types/tutorial010_py310.py hl[1:3] *}

接著你可以宣告一個變數為 `Person` 型別：

        assertEquals("plugin", artifact.getName());
        assertEquals("", artifact.getVersion());
    }

    // Test inner classes
    @Test
    public void test_Artifact_constructor() {
        Artifact artifact = new Artifact("test", "1.0.0", "http://test.com/test.jar");
        assertEquals("test", artifact.getName());

/**
 * Derived suite generators, split out of the suite builders so that they are available to GWT.
 *
 * @author George van den Driessche
 */
@GwtCompatible
@NullMarked
public final class DerivedCollectionGenerators {
  public static class MapEntrySetGenerator<K extends @Nullable Object, V extends @Nullable Object>
      implements TestSetGenerator<Entry<K, V>>, DerivedGenerator {

        for (String query : uniqueQueries) {
            assertTrue(testFacetInfo.getAddedQueries().contains(query));
        }
    }

    // Helper classes for testing
    private static class TestFacetInfo extends FacetInfo {
        private final List<String> addedQueries = new ArrayList<>();

        @Override
        public void addQuery(String s) {
            addedQueries.add(s);

    }

    // Helper methods for creating mock objects
    private SearchRequestParams createMockSearchRequestParams() {
        return new MockSearchRequestParams();
    }

    // Mock classes
    private static class MockFessConfig extends FessConfig.SimpleImpl {
        private static final long serialVersionUID = 1L;

        @Override
        public String getCookieSearchParameterRequiredKeys() {

val Project.testDistributionServerUrl: Provider<String>
    get() = gradleProperty(TEST_DISTRIBUTION_SERVER_URL)


// Controls the test distribution partition size. The test classes smaller than this value will be merged into a "partition"
val Project.maxTestDistributionPartitionSecond: Long?
    get() = systemProperty(TEST_DISTRIBUTION_PARTITION_SIZE).orNull?.toLong()

            else:
                # It would probably make more sense for all response classes to have an
                # explicit default status_code, and to extract it from them, instead of
                # doing this inspection tricks, that would probably be in the future
                # TODO: probably make status_code a default class attribute for all
                # responses in Starlette

 * which may be a subtype of the declaring class. For example:
 *
 * {@snippet :
 * Method getMethod = List.class.getMethod("get", int.class);
 * Invokable<List<String>, ?> invokable = new TypeToken<List<String>>() {}.method(getMethod);
 * assertEquals(TypeToken.of(String.class), invokable.getReturnType()); // Not Object.class!
 * assertEquals(new TypeToken<List<String>>() {}, invokable.getOwnerType());
 * }

     * bufferIndex, and thus headerStart, would be 4).(NOTE: If one where
     * looking for a way to improve perfomance this is precisly what you
     * would want to do as the jcifs.smb1.netbios.SocketXxxputStream classes
     * arraycopy all data read or written into a new buffer shifted over 4!)
     */

    byte command, flags;
    int headerStart, length, batchLevel, errorCode, flags2, tid, pid, uid, mid, wordCount, byteCount;

    @Nonnull
    PathScope getPathScope();

    /**
     * Returns a filter for the types of path (class-path, module-path, …) accepted by the tool.
     * For example, if a Java tools accepts only class-path elements, then the filter should return
     * {@code true} for {@link JavaPathType#CLASSES} and {@code false} for {@link JavaPathType#MODULES}.