code: def addClassToGraph(
              self, class_id, label=None, class_type=None, description=None
      ):
          
          assert class_id is not None
  
          self.graph.addTriple(
              class_id, self.globaltt['type'], self.globaltt['class'])
          if label is not None:
              self.graph.addTriple(
                  class_id, self.globaltt['label'], label, object_is_literal=True)
  
          if class_type is not None:
              self.graph.addTriple(class_id, self.globaltt['subclass_of'], class_type)
          if description is not None:
              self.graph.addTriple(
                  class_id, self.globaltt['description'], description,
                  object_is_literal=True)
docs: Any node added to the graph will get at least 3 triples:
          *(node, type, owl:Class) and
          *(node, label, literal(label))
          *if a type is added,
              then the node will be an OWL:subclassOf that the type
          *if a description is provided,
              it will also get added as a dc:description
          :param class_id:
          :param label:
          :param class_type:
          :param description:
          :return: