code: def create_conjunction_node(self, conjunction):
          
          node = BNode()
          type_triple = (node, RDF.type, self.spdx_namespace.ConjunctiveLicenseSet)
          self.graph.add(type_triple)
          licenses = self.licenses_from_tree(conjunction)
          for lic in licenses:
              member_triple = (node, self.spdx_namespace.member, lic)
              self.graph.add(member_triple)
          return node
docs: Return a node representing a conjunction of licenses.