code: def add_node(self, G, node_xml, node_attr, node_pid=None):
      # add a single node with attributes to the graph
  
      # get attributes and subattributues for node
      data = self.decode_attr_elements(node_attr, node_xml)
      data = self.add_parents(data, node_xml)  # add any parents
      if self.VERSION == "1.1":
          data = self.add_slices(data, node_xml)  # add slices
      else:
          data = self.add_spells(data, node_xml)  # add spells
      data = self.add_viz(data, node_xml)  # add viz
      data = self.add_start_end(data, node_xml)  # add start/end
  
      # find the node id and cast it to the appropriate type
      node_id = node_xml.get("id")
      if self.node_type is not None:
          node_id = self.node_type(node_id)
  
      # every node should have a label
      node_label = node_xml.get("label")
      data["label"] = node_label
  
      # parent node id
      node_pid = node_xml.get("pid", node_pid)
      if node_pid is not None:
          data["pid"] = node_pid
  
      # check for subnodes, recursive
      subnodes = node_xml.find(f"{{{self.NS_GEXF}}}nodes")
      if subnodes is not None:
          for node_xml in subnodes.findall(f"{{{self.NS_GEXF}}}node"):
              self.add_node(G, node_xml, node_attr, node_pid=node_id)
  
      G.add_node(node_id, **data)
  
imports: import itertools
  import time
  from xml.etree.ElementTree import Element, ElementTree, SubElement, register_namespace, tostring
  import networkx
  from networkx.utils import open_file
label_desc: Use image node_id 4 for calling the GEXFReader obj's underlying member method code with example usage: obj.add_node(G, node_xml, node_attr, node_pid) without return types