code: public TimezoneAssignment getTimezoneById(String tzid) {
  		for (TimezoneAssignment assignment : assignments) {
  			VTimezone component = assignment.getComponent();
  			if (component == null) {
  				continue;
  			}
  
  			String componentId = ValuedProperty.getValue(component.getTimezoneId());
  			if (tzid.equals(componentId)) {
  				return assignment;
  			}
  		}
  		return null;
  	}
docs: Gets the timezone whose {@link VTimezone} component contains a
  {@link TimezoneId} property with the given value.
  @param tzid the value of the {@link TimezoneId} property
  @return the timezone or null if not found