other middlewares in the [Advanced User Guide: Advanced Middleware](../advanced/middleware.md){.internal-link target=_blank}.

You will read about how to handle <abbr title="Cross-Origin Resource Sharing">CORS</abbr> with a middleware in the next section....

We are already halfway there.

We just need to add a *path operation* for the user/client to actually send the `username` and `password`.

      resetContainer(mapEntry(k0(), v0()), mapEntry(k0(), v1()), mapEntry(k0(), v0()));
      List<V> expectedValues = copyToList(values);

      Entry<K, Collection<V>> asMapEntry = multimap().asMap().entrySet().iterator().next();
      List<V> asMapValue = (List<V>) asMapEntry.getValue();
      asMapValue.remove(i);
      expectedValues.remove(i);

      assertGet(k0(), expectedValues);
    }
  }

  public void testKeySetIteratorRemove() {
    int key0Count = multimap().get(k0()).size();
    Iterator<K> keyItr = multimap().keySet().iterator();
    while (keyItr.hasNext()) {
      if (keyItr.next().equals(k0())) {
        keyItr.remove();
      }
    }
    assertEquals(getNumElements() - key0Count, multimap().size());
    assertGet(k0());
  }

    Map<String, Collection<Integer>> map;
    try {
      map = makePopulatedMap();
    } catch (UnsupportedOperationException e) {
      return;
    }
    String keyToRemove = map.keySet().iterator().next();
    if (supportsRemove) {
      int initialSize = map.size();
      // var oldValue = map.get(keyToRemove);
      map.remove(keyToRemove);
      // This line doesn't hold - see the Javadoc comments above.

	f.Add(b.Bytes())

	f.Fuzz(func(t *testing.T, b []byte) {
		r := NewReader(bytes.NewReader(b))
		type file struct {
			header  *Header
			content []byte
		}
		files := []file{}
		for {
			hdr, err := r.Next()
			if err == io.EOF {
				break
			}
			if err != nil {
				return
			}
			buf := bytes.NewBuffer(nil)
			if _, err := io.Copy(buf, r); err != nil {
				continue
			}

   *     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**

   *     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**

 *
 * Each derivation can capture the next value or any intermediate objects for later closing.
 *
 * <p>A step can be the input to at most one derived step. Once you transform its value, catch its
 * exception, or combine it with others, you cannot do anything else with it, including declare it
 * to be the last step of the pipeline.
 *
 * <h4>Transforming</h4>
 *

                    Iterator<Item> right = ((ListItem) item).iterator();

                    while (left.hasNext() || right.hasNext()) {
                        Item l = left.hasNext() ? left.next() : null;
                        Item r = right.hasNext() ? right.next() : null;

                        // if this is shorter, then invert the compare and mul with -1