* for that key. The subclass should not call {@link #createCollection()} directly, and a new
 * instance should be created every time the method is called.
 *
 * <p>For example, the subclass could pass a {@link java.util.TreeMap} during construction, and
 * {@link #createCollection()} could return a {@link java.util.TreeSet}, in which case the
 * multimap's iterators would propagate through the keys and values in sorted order.
 *

 * for that key. The subclass should not call {@link #createCollection()} directly, and a new
 * instance should be created every time the method is called.
 *
 * <p>For example, the subclass could pass a {@link java.util.TreeMap} during construction, and
 * {@link #createCollection()} could return a {@link java.util.TreeSet}, in which case the
 * multimap's iterators would propagate through the keys and values in sorted order.
 *

   * There is no need to use this method on a {@link Map} implementation that already has a
   * corresponding {@link Set} implementation (such as {@link java.util.HashMap} or {@link
   * java.util.TreeMap}).
   *
   * <p>Each method invocation on the set returned by this method results in exactly one method
   * invocation on the backing map or its {@code keySet} view, with one exception. The {@code

   * There is no need to use this method on a {@link Map} implementation that already has a
   * corresponding {@link Set} implementation (such as {@link java.util.HashMap} or {@link
   * java.util.TreeMap}).
   *
   * <p>Each method invocation on the set returned by this method results in exactly one method
   * invocation on the backing map or its {@code keySet} view, with one exception. The {@code