docstr: Serialize graph G in GraphML to the stream.
docstr_tok: ["Serialize","graph","G","in","GraphML","to","the","stream","."]
code: def add_graph_element(self, G):
      """
      Serialize graph G in GraphML to the stream.
      """
      if G.is_directed():
          default_edge_type = "directed"
      else:
          default_edge_type = "undirected"
  
      graphid = G.graph.pop("id", None)
      if graphid is None:
          graph_element = self.myElement(
              "graph", edgedefault=default_edge_type
          )
      else:
          graph_element = self.myElement(
              "graph", edgedefault=default_edge_type, id=graphid
          )
      default = {}
      data = {
          k: v
          for (k, v) in G.graph.items()
          if k not in ["node_default", "edge_default"]
      }
      self.add_attributes("graph", graph_element, data, default)
      self.add_nodes(G, graph_element)
      self.add_edges(G, graph_element)
  
      # self.attributes contains a mapping from XML Objects to a list of
      # data that needs to be added to them.
      # We postpone processing in order to do type inference/generalization.
      # See self.attr_type
      for xml_obj, data in self.attributes.items():
          for k, v, scope, default in data:
              xml_obj.append(
                  self.add_data(
                      str(k),
                      self.attr_type(k, scope, v),
                      str(v),
                      scope,
                      default,
                  )
              )
      self.xml.append(graph_element)
  
imports: import warnings
  from collections import defaultdict
  import networkx
  from networkx.utils import open_file
label_desc: Use image node_id 9 for calling the GraphMLWriter obj's underlying member method code with example usage: obj.add_graph_element(G) without return types