* Instead ✨ **use `Union[SomeType, None]`** ✨.

Both are equivalent and underneath they are the same, but I would recommend `Union` instead of `Optional` because the word "**optional**" would seem to imply that the value is optional, and it actually means "it can be `None`", even if it's not optional and is still required.

I think `Union[SomeType, None]` is more explicit about what it means.

   * Returns an {@link ImmutableSortedSet} containing the same values in the given domain
   * {@linkplain RangeSet#contains contained} by this range set.
   *
   * <p><b>Note:</b> {@code a.asSet(d).equals(b.asSet(d))} does not imply {@code a.equals(b)}! For
   * example, {@code a} and {@code b} could be {@code [2..4]} and {@code (1..5)}, or the empty
   * ranges {@code [3..3)} and {@code [4..4)}.
   *

    <exportedPackage>org.eclipse.aether.graph</exportedPackage>
    <exportedPackage>org.eclipse.aether.impl</exportedPackage>
    <exportedPackage>org.eclipse.aether.internal.impl</exportedPackage>
    <exportedPackage>org.eclipse.aether.installation</exportedPackage>
    <exportedPackage>org.eclipse.aether.metadata</exportedPackage>
    <exportedPackage>org.eclipse.aether.repository</exportedPackage>

import org.apache.maven.execution.MavenSession;
import org.apache.maven.impl.DefaultArtifact;
import org.apache.maven.impl.DefaultArtifactCoordinatesFactory;
import org.apache.maven.impl.DefaultArtifactResolver;
import org.apache.maven.impl.DefaultModelVersionParser;
import org.apache.maven.impl.DefaultRepositoryFactory;
import org.apache.maven.impl.DefaultVersionParser;
import org.apache.maven.impl.InternalSession;

import org.apache.maven.cling.invoker.LookupInvoker;
import org.apache.maven.cling.utils.CLIReportingUtils;
import org.jline.builtins.ConfigurationPath;
import org.jline.console.impl.Builtins;
import org.jline.console.impl.SimpleSystemRegistryImpl;
import org.jline.console.impl.SystemRegistryImpl;
import org.jline.keymap.KeyMap;
import org.jline.reader.Binding;
import org.jline.reader.EndOfFileException;
import org.jline.reader.LineReader;

import org.apache.maven.impl.DefaultArtifactCoordinatesFactory;
import org.apache.maven.impl.DefaultArtifactResolver;
import org.apache.maven.impl.DefaultModelVersionParser;
import org.apache.maven.impl.DefaultRepositoryFactory;
import org.apache.maven.impl.DefaultVersionParser;
import org.apache.maven.impl.DefaultVersionRangeResolver;
import org.apache.maven.impl.InternalSession;

    };

    abstract ExecutionListWrapper newExecutionList();
  }

  private ThreadPoolExecutor executorService;
  private CountDownLatch listenerLatch;
  private ExecutionListWrapper list;

  @Param Impl impl;

  @Param({"1", "5", "10"})
  int numListeners;

  private final Runnable listener =
      new Runnable() {
        @Override
        public void run() {
          listenerLatch.countDown();

import org.apache.maven.impl.DefaultArtifactCoordinatesFactory;
import org.apache.maven.impl.DefaultArtifactResolver;
import org.apache.maven.impl.DefaultModelVersionParser;
import org.apache.maven.impl.DefaultRepositoryFactory;
import org.apache.maven.impl.DefaultVersionParser;
import org.apache.maven.impl.DefaultVersionRangeResolver;
import org.apache.maven.impl.InternalSession;

import org.apache.maven.di.Injector;
import org.apache.maven.di.Key;
import org.apache.maven.di.Scope;
import org.apache.maven.di.impl.Binding;
import org.apache.maven.di.impl.DIException;
import org.apache.maven.di.impl.Dependency;
import org.apache.maven.di.impl.InjectorImpl;
import org.apache.maven.execution.scope.internal.MojoExecutionScope;
import org.apache.maven.session.scope.internal.SessionScope;

import org.apache.maven.execution.MavenSession;
import org.apache.maven.impl.model.reflection.IntrospectionException;
import org.apache.maven.internal.impl.DefaultLookup;
import org.apache.maven.internal.impl.DefaultMojoExecution;
import org.apache.maven.internal.impl.DefaultProject;
import org.apache.maven.internal.impl.DefaultSession;
import org.apache.maven.internal.impl.InternalMavenSession;
import org.apache.maven.model.Build;