docs: def add(self, key, value, lang=None):
          """ Add a triple to the graph related to this node
  
          :param key: Predicate of the triple
          :param value: Object of the triple
          :param lang: Language of the triple if applicable
          """
          if not isinstance(value, Literal) and lang is not None:
              value = Literal(value, lang=lang)
          elif not isinstance(value, (BNode, URIRef)):
              value, _type = term._castPythonToLiteral(value)
              if _type is None:
                  value = Literal(value)
              else:
                  value = Literal(value, datatype=_type)
          self.graph.add((self.asNode(), key, value))