code: public ReferenceBuilder withNoValue(PropertyIdValue propertyIdValue) {
  		getSnakList(propertyIdValue).add(
  				factory.getNoValueSnak(propertyIdValue));
  		return getThis();
  	}
docs: Adds a {@link NoValueSnak} with the given property to the constructed
  reference.
  <p>
  Note that it might not be meaningful to use {@link NoValueSnak} in a
  reference. It is usually implicitly assumed that all snaks that are not
  given have no value for a particular reference. Otherwise one would need
  large numbers of {@link NoValueSnak} entries for every reference!
  
  @param propertyIdValue
  the property of the snak
  @return builder object to continue construction