{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## Add the background task

Inside of your *path operation function*, pass your task function to the *background tasks* object with the method `.add_task()`:

{* ../../docs_src/background_tasks/tutorial001.py hl[14] *}

`.add_task()` receives as arguments:

* A task function to be run in the background (`write_notification`).

@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class PairedStatsAccumulator {

  // These fields must satisfy the requirements of PairedStats' constructor as well as those of the
  // stat methods of this class.
  private final StatsAccumulator xStats = new StatsAccumulator();
  private final StatsAccumulator yStats = new StatsAccumulator();
  private double sumOfProductsOfDeltas = 0.0;

    } else {
      return ~index;
    }
  }

  // Pretend the comparator can compare anything. If it turns out it can't
  // compare two elements, it'll throw a CCE. Only methods that are specified to
  // throw CCE should call this.
  @SuppressWarnings("unchecked")
  Comparator<Object> unsafeComparator() {
    return (Comparator<Object>) comparator;
  }

   * `streamId`.
   *
   * @param streamId client-initiated stream ID.  Must be an odd number.
   * @param promisedStreamId server-initiated stream ID.  Must be an even number.
   * @param requestHeaders minimally includes `:method`, `:scheme`, `:authority`, and `:path`.
   */
  @Throws(IOException::class)
  fun pushPromise(
    streamId: Int,
    promisedStreamId: Int,
    requestHeaders: List<Header>,
  ) {
    this.withLock {

			}
			lastErr = err
			break
		}
	}(user.ID)

	wg.Add(1)
	go func() {
		defer wg.Done()
		for range closeValid {
			for i := 0; i < loopCount; i++ {
				pdb.Close() // the Close method must can be call multiple times
				atomic.CompareAndSwapInt64(&closeFinishedAt, 0, time.Now().UnixNano())
			}
		}
	}()

	wg.Wait()
	var tmp User

	if err := buf.UnreadByte(); err == nil {
		t.Fatal("UnreadByte: expected error, got nil")
	}
}

// verify that copying from an empty reader always has the same results,
// regardless of the presence of a WriteTo method.
func TestReaderCopyNothing(t *testing.T) {
	type nErr struct {
		n   int64
		err error
	}
	type justReader struct {
		io.Reader
	}
	type justWriter struct {
		io.Writer
	}

#### Blocking APIs

Blocking APIs are convenient because you get top-to-bottom procedural code without indirection. Network calls work like regular method calls: ask for data and it is returned. If the request fails, you get a stacktrace right where the call was made.

        assertThat(i.next().getKey(), is(nullValue()));
        assertThat(i.next().getKey(), is("1"));
        assertThat(i.next().getKey(), is("2"));
    }

    /**
     * Test method for {@link org.seasar.util.collection.ArrayIterator#remove()}
     * .
     */
    @Test
    public void testArrayIteratorRemoveException() {
        exception.expect(ClIllegalStateException.class);

'4.4.1'\nconst DATA_KEY           = 'bs.scrollspy'\nconst EVENT_KEY          = `.${DATA_KEY}`\nconst DATA_API_KEY       = '.data-api'\nconst JQUERY_NO_CONFLICT = $.fn[NAME]\n\nconst Default = {\n  offset : 10,\n  method : 'auto',\n  target : ''\n}\n\nconst DefaultType = {\n  offset : 'number',\n  method : 'string',\n  target : '(string|element)'\n}\n\nconst Event = {\n  ACTIVATE      : `activate${EVENT_KEY}`,\n  SCROLL        : `scroll${EVENT_KEY}`,\n  LOAD_DATA_API : `load${EVENT_KEY}${DATA_API_KEY}`\n}\n\nconst...

    }
  }

  public static class ImmutableSetWithBadHashesGenerator extends TestCollidingSetGenerator
      // Work around a GWT compiler bug.  Not explicitly listing this will
      // cause the createArray() method missing in the generated javascript.
      // TODO: Remove this once the GWT bug is fixed.
      implements TestCollectionGenerator<Object> {
    @Override
    public Set<Object> create(Object... elements) {