code: @SuppressWarnings("unchecked")
    public static <E> ImmutableSortedMultiset<E> copyOf(
        Comparator<? super E> comparator, Iterable<? extends E> elements) {
      if (elements instanceof ImmutableSortedMultiset) {
        @SuppressWarnings("unchecked") // immutable collections are always safe for covariant casts
        ImmutableSortedMultiset<E> multiset = (ImmutableSortedMultiset<E>) elements;
        if (comparator.equals(multiset.comparator())) {
          if (multiset.isPartialView()) {
            return copyOfSortedEntries(comparator, multiset.entrySet().asList());
          } else {
            return multiset;
          }
        }
      }
      return new ImmutableSortedMultiset.Builder<E>(comparator).addAll(elements).build();
    }
docs: Returns an immutable sorted multiset containing the given elements sorted by the given {@code
  Comparator}. This method iterates over {@code elements} at most once.
  
  <p>Despite the method name, this method attempts to avoid actually copying the data when it is
  safe to do so. The exact circumstances under which a copy will or will not be performed are
  undocumented and subject to change.
  
  @throws NullPointerException if {@code comparator} or any of {@code elements} is null