Spliterator.SIZED
            | (entrySpliterator.characteristics()
                & (Spliterator.ORDERED | Spliterator.NONNULL | Spliterator.IMMUTABLE)),
        multiset.size());
  }

  /** An implementation of {@link Multiset#size}. */
  static int linearTimeSizeImpl(Multiset<?> multiset) {
    long size = 0;

import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.BinaryOperator;
import java.util.stream.Collector;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to {@link Map} instances (including instances of {@link