import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link NavigableMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> as with any sorted collection, you are strongly advised not to use a {@link

   * avoid memory leaks when an element is no longer necessary.
   *
   * <p>This method accepts an array with element type {@code @Nullable T}, but callers must pass an
   * array whose contents are initially non-null. The {@code @Nullable} annotation indicates that
   * this method will write nulls into the array during iteration.
   *

   * method returns instances of a different class than {@code factory.get()} does.
   *
   * <p>The multimap is serializable if {@code map}, {@code factory}, the collections generated by
   * {@code factory}, and the multimap contents are all serializable.
   *
   * <p>The multimap is not threadsafe when any concurrent operations update the multimap, even if
   * {@code map} and the instances generated by {@code factory} are. Concurrent read operations will

 *
 * <p>The caches produced by {@code CacheBuilder} are serializable, and the deserialized caches
 * retain all the configuration properties of the original cache. Note that the serialized form does
 * <i>not</i> include cache contents, but only configuration.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/CachesExplained">caching</a> for a higher-level
 * explanation.
 *