}
    }
    return true;
  }

  /**
   * Checks all the properties that should always hold of a map. Also calls {@link
   * #assertMoreInvariants} to check invariants that are peculiar to specific implementations.
   *
   * @see #assertMoreInvariants
   * @param map the map to check.
   */
  protected final void assertInvariants(Map<K, V> map) {
    Set<K> keySet = map.keySet();