}

  /**
   * Returns a {@link Stream} containing the elements of the first stream, followed by the elements
   * of the second stream, and so on.
   *
   * <p>This is equivalent to {@code Stream.of(streams).flatMap(stream -> stream)}, but the returned
   * stream may perform better.
   *
   * @see Stream#concat(Stream, Stream)
   */
  @SuppressWarnings("unchecked") // could probably be avoided with a forwarding Spliterator

            userManual.getSamples().convention(layout.getProjectDirectory().dir("src/samples"));
            userManual.getStagedDocumentation().convention(userguideFlattenSources.flatMap(task -> (DirectoryProperty) task.getExtensions().getExtraProperties().get("destinationDirectory")));
            userManual.getRenderedDocumentation().from(userguide);
        });
    }

        return request.getProfiles().stream()
                .filter(profile -> activeProfileId.contains(profile.getId()))
                .map(ModelBase::getProperties)
                .flatMap(properties -> properties.entrySet().stream())
                .filter(e -> e.getValue() != null)
                .collect(Collectors.toMap(

      V output(@ParametricNullness K key, @ParametricNullness V value) {
        return value;
      }
    };
  }

  @Override
  Spliterator<V> valueSpliterator() {
    return CollectSpliterators.flatMap(
        map.values().spliterator(), Collection::spliterator, Spliterator.SIZED, size());
  }

  /*
   * TODO(kevinb): should we copy this javadoc to each concrete class, so that

```
scala> val file = sc.textFile("s3a://testbucket/testdata")
file: org.apache.spark.rdd.RDD[String] = s3a://testbucket/testdata MapPartitionsRDD[1] at textFile at <console>:24

scala> val counts = file.flatMap(line => line.split(" ")).map(word => (word, 1)).reduceByKey(_ + _)
counts: org.apache.spark.rdd.RDD[(String, Int)] = ShuffledRDD[4] at reduceByKey at <console>:25

scala> counts.saveAsTextFile("s3a://testbucket/wordcount")

        }

        request.setToolchains(
                Optional.ofNullable(context.effectiveToolchains).map(PersistedToolchains::getToolchains).stream()
                        .flatMap(List::stream)
                        .map(ToolchainModel::new)
                        .collect(Collectors.groupingBy(ToolchainModel::getType)));

      }
    };
  }

  @Override
  @GwtIncompatible("Spliterator")
  Spliterator<Entry<K, V>> entrySpliterator() {
    return CollectSpliterators.flatMap(
        asMap().entrySet().spliterator(),
        keyToValueCollectionEntry -> {
          K key = keyToValueCollectionEntry.getKey();
          Collection<V> valueCollection = keyToValueCollectionEntry.getValue();

    }
  }

  static <E extends @Nullable Object> Spliterator<E> spliteratorImpl(Multiset<E> multiset) {
    Spliterator<Entry<E>> entrySpliterator = multiset.entrySet().spliterator();
    return CollectSpliterators.flatMap(
        entrySpliterator,
        (Entry<E> entry) -> Collections.nCopies(entry.getCount(), entry.getElement()).spliterator(),
        Spliterator.SIZED
            | (entrySpliterator.characteristics()

 * public class CustomPackagingProvider implements PackagingProvider {
 *     public Collection<Packaging> provides() {
 *         return Arrays.asList(
 *             packaging("docker-image"),
 *             packaging("flatpak")
 *         );
 *     }
 * }
 * </pre>
 *
 * @see org.apache.maven.api.Packaging
 * @see org.apache.maven.api.spi.ExtensibleEnumProvider
 * @since 4.0.0
 */
@Experimental
@Consumer
@Named