code: private ImmutableList<TargetAtom> getRefCQ(ForeignKeyConstraint fk) {
          ImmutableTerm sub = generateSubject(fk.getRelation(), true);
  		ImmutableTerm obj = generateSubject(fk.getReferencedRelation(), true);
  
  		TargetAtom atom = getAtom(getReferencePropertyIRI(fk), sub, obj);
  		return ImmutableList.of(atom);
  	}
docs: Definition row graph: an RDF graph consisting of the following triples:
  
  - a reference triple for each <column name list> in a table's foreign keys where none of the column values is NULL.