// here too.
  static final String ERROR_MODIFIABLE_SET = "Set returned is unexpectedly modifiable";
  static final String ERROR_SELF_LOOP = "self-loops are not allowed";
  static final String ERROR_ADDED_SELF_LOOP = "Should not be allowed to add a self-loop edge.";

  /** Creates and returns an instance of the graph to be tested. */
  abstract Graph<Integer> createGraph();

  /**

  private static final String ERROR_PARALLEL_EDGE = "connected by a different edge";
  private static final String ERROR_NEGATIVE_COUNT = "is non-negative";
  static final String ERROR_SELF_LOOP = "self-loops are not allowed";

  @Test
  public void transitiveClosure_directedGraph_addSelfLoopsAlways() {
    MutableGraph<Integer> directedGraph = GraphBuilder.directed().allowsSelfLoops(false).build();

        when(config.getPid()).thenReturn(12345);
        when(config.getSendBufferSize()).thenReturn(65536);

        target = new SmbPipeHandleImpl(pipe);
    }

    @Test
    @DisplayName("unwrap returns self for assignable type; throws for incompatible and null")
    void testUnwrap() {
        // Happy path: unwrap to concrete type
        SmbPipeHandleImpl unwrapped = target.unwrap(SmbPipeHandleImpl.class);

```

那它就是一個「callable」。

## 以類別作為相依性 { #classes-as-dependencies_1 }

你可能已經注意到，建立一個 Python 類別的實例時，你用的語法也是一樣的。

例如：

```Python
class Cat:
    def __init__(self, name: str):
        self.name = name


fluffy = Cat(name="Mr Fluffy")
```

在這個例子中，`fluffy` 是 `Cat` 類別的一個實例。

而要建立 `fluffy`，你其實是在「呼叫」`Cat`。

所以，Python 類別本身也是一種 **callable**。

 * {@link EndpointPair} of an undirected edge is an unordered pair of nodes ({@link #nodeU()} and
 * {@link #nodeV()}).
 *
 * <p>The edge is a self-loop if, and only if, the two endpoints are equal.
 *
 * @author James Sexton
 * @since 20.0
 */
@Immutable(containerOf = {"N"})
public abstract class EndpointPair<N> implements Iterable<N> {
  private final N nodeU;

@Named
public class BootstrapCoreExtensionManager {
    public static final String STRATEGY_PARENT_FIRST = "parent-first";
    public static final String STRATEGY_PLUGIN = "plugin";
    public static final String STRATEGY_SELF_FIRST = "self-first";

    private final Logger log = LoggerFactory.getLogger(getClass());

    private final DefaultPluginDependenciesResolver pluginDependenciesResolver;

        // Close of try-with-resources should call close on the mock
        verify(tree, times(1)).close();
    }

    @Test
    @DisplayName("unwrap: returns self for compatible type and throws for incompatible")
    @SuppressWarnings({ "rawtypes", "unchecked" })
    void testUnwrap() {
        SmbSessionImpl session = newSession();

@Named
public class BootstrapCoreExtensionManager {
    public static final String STRATEGY_PARENT_FIRST = "parent-first";
    public static final String STRATEGY_PLUGIN = "plugin";
    public static final String STRATEGY_SELF_FIRST = "self-first";

    private final Logger log = LoggerFactory.getLogger(getClass());

    private final DefaultPluginDependenciesResolver pluginDependenciesResolver;

	if topE == nil {
		scannerLogIf(GlobalContext, errors.New("forceCompact: root not found"))
		return
	}
	// If off by 2 orders of magnitude, compact self and log error.
	if len(topE.Children) > dataScannerForceCompactAtFolders {
		// If we still have too many children, compact self.

    }

    @Test
    void testSelfReferencingDependencyInRawModel() throws Exception {
        SimpleProblemCollector result = validateRaw("raw-model/self-referencing.xml");

        assertViolations(result, 1, 0, 0);

        assertEquals(