code: public void addValueSet(ValueSet theValueSet) {
  		Validate.notBlank(theValueSet.getUrl(), "theValueSet.getUrl() must not return a value");
  		myValueSets.put(theValueSet.getUrl(), theValueSet);
  	}
docs: Add a new ValueSet resource which will be available to the validator. Note that
  {@link ValueSet#getUrl() the URL field) in this resource must contain a value as this
  value will be used as the logical URL.