code: def create_creation_info(self):
          
          ci_node = BNode()
          # Type property
          type_triple = (ci_node, RDF.type, self.spdx_namespace.CreationInfo)
          self.graph.add(type_triple)
  
          created_date = Literal(self.document.creation_info.created_iso_format)
          created_triple = (ci_node, self.spdx_namespace.created, created_date)
          self.graph.add(created_triple)
  
          creators = self.creators()
          for creator in creators:
              self.graph.add((ci_node, self.spdx_namespace.creator, creator))
  
          if self.document.creation_info.has_comment:
              comment_node = Literal(self.document.creation_info.comment)
              comment_triple = (ci_node, RDFS.comment, comment_node)
              self.graph.add(comment_triple)
  
          return ci_node
docs: Add and return a creation info node to graph