code: public static <T extends Throwable, C extends Throwable> Matcher<T> withCause(Matcher<C> matcher) {
          return IsThrowable.withCause(matcher);
      }
docs: Throwable matcher to be used with {@link #isThrowable(Class, Matcher)}
  @see #isThrowable(Class, Matcher)
  @param matcher the cause matcher
  @param <T> the throwable type
  @param <C> the cause type
  @return the matcher