* to the set.
   *
   * <p><b>Warning:</b> This method assumes that for any instance {@code k} of key type {@code K},
   * {@code k.equals(k2)} implies that {@code k2} is also of type {@code K}. Using a key type for
   * which this may not hold, such as {@code ArrayList}, may risk a {@code ClassCastException} when
   * calling methods on the resulting map view.
   *

   * to the set.
   *
   * <p><b>Warning:</b> This method assumes that for any instance {@code k} of key type {@code K},
   * {@code k.equals(k2)} implies that {@code k2} is also of type {@code K}. Using a key type for
   * which this may not hold, such as {@code ArrayList}, may risk a {@code ClassCastException} when
   * calling methods on the resulting map view.
   *