* set. See also {@link #forMap(Map)}, which throws an exception in this case.
   *
   * <p><b>Java 8+ users:</b> you can just write the lambda expression {@code k ->
   * map.getOrDefault(k, defaultValue)} instead.
   *
   * @param map source map that determines the function behavior
   * @param defaultValue the value to return for inputs that aren't map keys

   * set. See also {@link #forMap(Map)}, which throws an exception in this case.
   *
   * <p><b>Java 8+ users:</b> you can just write the lambda expression {@code k ->
   * map.getOrDefault(k, defaultValue)} instead.
   *
   * @param map source map that determines the function behavior
   * @param defaultValue the value to return for inputs that aren't map keys