code: public ReferenceBuilder withSomeValue(PropertyIdValue propertyIdValue) {
  		getSnakList(propertyIdValue).add(
  				factory.getSomeValueSnak(propertyIdValue));
  		return getThis();
  	}
docs: Adds a {@link SomeValueSnak} with the given property to the constructed
  reference.
  <p>
  Note that it might not be meaningful to use {@link SomeValueSnak} in a
  reference, depending on the policies of the wiki.
  
  @param propertyIdValue
  the property of the snak
  @return builder object to continue construction