code: public PaymillList<Subscription> list( Subscription.Filter filter, Subscription.Order order ) {
      return this.list( filter, order, null, null );
    }
docs: This function returns a {@link List} of PAYMILL {@link Subscription} objects.<br>
  <br>
  In which order this list is returned depends on the optional parameters. If <code>null</code> is given, no filter
  or order will be applied.
  
  @param filter {@link com.paymill.models.Subscription.Filter} or <code>null</code>
  @param order {@link com.paymill.models.Subscription.Order} or <code>null</code>
  @return {@link PaymillList} which contains a {@link List} of PAYMILL {@link Subscription}s and their total count.