code: def get_node (self, url_data):
          
          if not url_data.url:
              return None
          elif url_data.url in self.nodes:
              return None
          node = {
              "url": url_data.url,
              "parent_url": url_data.parent_url,
              "id": self.nodeid,
              "label": quote(url_data.title if url_data.title else url_data.name),
              "extern": 1 if url_data.extern else 0,
              "checktime": url_data.checktime,
              "size": url_data.size,
              "dltime": url_data.dltime,
              "edge": quote(url_data.name),
              "valid": 1 if url_data.valid else 0,
          }
          self.nodes[node["url"]] = node
          self.nodeid += 1
          return node
docs: Return new node data or None if node already exists.