code: def create_annotation_node(self, annotation):
          
          annotation_node = URIRef(str(annotation.spdx_id))
          type_triple = (annotation_node, RDF.type, self.spdx_namespace.Annotation)
          self.graph.add(type_triple)
  
          annotator_node = Literal(annotation.annotator.to_value())
          self.graph.add((annotation_node, self.spdx_namespace.annotator, annotator_node))
          annotation_date_node = Literal(annotation.annotation_date_iso_format)
          annotation_triple = (annotation_node, self.spdx_namespace.annotationDate, annotation_date_node)
          self.graph.add(annotation_triple)
          if annotation.has_comment:
              comment_node = Literal(annotation.comment)
              comment_triple = (annotation_node, RDFS.comment, comment_node)
              self.graph.add(comment_triple)
          annotation_type_node = Literal(annotation.annotation_type)
          annotation_type_triple = (annotation_node, self.spdx_namespace.annotationType, annotation_type_node)
          self.graph.add(annotation_type_triple)
  
          return annotation_node
docs: Return an annotation node.