code: public static ConceptId getInstance(String propId, String propertyName, Metadata metadata) {
          return getInstance(propId, propertyName, null, metadata);
      }
docs: Returns a concept propId with the given proposition propId and property name.
  
  @param propId a proposition propId {@link String}. Cannot be
  <code>null</code>.
  @param propertyName a property name {@link String}.
  @return a {@link PropDefConceptId}.