code: def package_verif_node(self, package):
          
          verif_node = BNode()
          type_triple = (verif_node, RDF.type, self.spdx_namespace.PackageVerificationCode)
          self.graph.add(type_triple)
          value_triple = (verif_node, self.spdx_namespace.packageVerificationCodeValue, Literal(package.verif_code))
          self.graph.add(value_triple)
          excl_file_nodes = map(
              lambda excl: Literal(excl), package.verif_exc_files)
          excl_predicate = self.spdx_namespace.packageVerificationCodeExcludedFile
          excl_file_triples = [(verif_node, excl_predicate, xcl_file) for xcl_file in excl_file_nodes]
          for trp in excl_file_triples:
              self.graph.add(trp)
          return verif_node
docs: Return a node representing package verification code.