code: public Url setUrl(String url) {
  		Url property = (url == null) ? null : new Url(url);
  		setUrl(property);
  		return property;
  	}
docs: Sets the location of a more dynamic, alternate representation of the
  calendar (such as a website that allows you to interact with the calendar
  data).
  @param url the URL or null to remove
  @return the property object that was created
  @see <a
  href="http://tools.ietf.org/html/draft-ietf-calext-extensions-01#page-7">draft-ietf-calext-extensions-01
  p.7</a>