result.append("Not listening on called name");
                break;
            case NOT_LISTENING_CALLING:
                result.append("Not listening for calling name");
                break;
            case CALLED_NOT_PRESENT:
                result.append("Called name not present");
                break;
            case NO_RESOURCES:
                result.append("Called name present, but insufficient resources");

import jcifs.SmbResource;

/**
 * Tests for {@link DirFileEntryAdapterIterator}.
 *
 * This test class verifies the basic functionality of DirFileEntryAdapterIterator.
 * Due to the iterator's constructor calling advance() immediately, which requires
 * the adapt() method to be functional, we test the behavior using simple mock
 * scenarios that don't require complex filter setups.
 */
@ExtendWith(MockitoExtension.class)

  /**
   * Any interruption that happens as a result of calling interruptTask will arrive before this
   * method is called. Complete Futures here.
   */
  abstract void afterRanInterruptiblySuccess(@ParametricNullness T result);

  /**
   * Any interruption that happens as a result of calling interruptTask will arrive before this
   * method is called. Complete Futures here.
   */

        // and a mock file that throws an exception when getAttributes is called
        SmbException expectedException = new SmbException("Failed to get attributes");
        when(mockFile.getAttributes()).thenThrow(expectedException);

        // When calling accept
        // Then an SmbException should be thrown
        SmbException thrown = assertThrows(SmbException.class, () -> {

    }

    @ParameterizedTest(name = "session error {1} -\\u003e {2}")
    @CsvSource({ "-1,Connection refused", "0x80,Not listening on called name", "0x81,Not listening for calling name",
            "0x82,Called name not present", "0x83,Called name present, but insufficient resources", "0x8F,Unspecified error",
            "999,Unknown error code: 999" })
    @DisplayName("getErrorString for SSN service errors")

     * cancelled.
     */
    @Nullable Executor delegate;

    /**
     * Set before calling delegate.execute(); set to null once run, so that it can be GCed; this
     * object may live on after, if submitAsync returns an incomplete future.
     */
    @Nullable Runnable task;

    /** Thread that called execute(). Set in execute, cleared when delegate.execute() returns. */
    @LazyInit @Nullable Thread submitting;

    this.closeables = closeables;
  }

  /**
   * Returns a future that finishes when this step does. Calling {@code get()} on the returned
   * future returns {@code null} if the step is successful or throws the same exception that would
   * be thrown by calling {@code finishToFuture().get()} if this were the last step. Calling {@code
   * cancel()} on the returned future has no effect on the {@code ClosingFuture} pipeline.
   *

    return super.pendingToString();
  }

  /**
   * Must be called at the end of each subclass's constructor. This method performs the "real"
   * initialization; we can't put this in the constructor because, in the case where futures are
   * already complete, we would not initialize the subclass before calling {@link
   * #collectValueFromNonCancelledFuture}. As this is called after the subclass is constructed,

   * in a {@code RuntimeException}. <b>Note:</b> Be sure to declare all of the checked exception
   * types your try block can throw when calling an overload of this method so as to avoid losing
   * the original exception type.
   *
   * <p>This method always throws, and as such should be called as {@code throw closer.rethrow(e);}
   * to ensure the compiler knows that it will throw.
   *

Actually, all (or most) of the web frameworks work in this same way.

You never call those functions directly. They are called by your framework (in this case, **FastAPI**).