import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.Iterables.transform;
import static com.google.common.collect.Iterators.mergeSorted;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Supplier;
import java.io.Serializable;
import java.util.Comparator;

import static com.google.common.collect.Iterables.find;
import static com.google.common.collect.Iterables.frequency;
import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.common.collect.Iterables.mergeSorted;
import static com.google.common.collect.Iterables.removeIf;
import static com.google.common.collect.Iterables.skip;
import static com.google.common.collect.Iterables.tryFind;

   * returned first.
   *
   * @since 11.0
   */
  public static <T extends @Nullable Object> UnmodifiableIterator<T> mergeSorted(
      Iterable<? extends Iterator<? extends T>> iterators, Comparator<? super T> comparator) {
    checkNotNull(iterators, "iterators");
    checkNotNull(comparator, "comparator");