code: def generate_graphml(
      G,
      encoding="utf-8",
      prettyprint=True,
      named_key_ids=False,
      edge_id_from_attribute=None,
  ):
      """Generate GraphML lines for G
  
      Parameters
      ----------
      G : graph
         A networkx graph
      encoding : string (optional)
         Encoding for text data.
      prettyprint : bool (optional)
         If True use line breaks and indenting in output XML.
      named_key_ids : bool (optional)
         If True use attr.name as value for key elements' id attribute.
      edge_id_from_attribute : dict key (optional)
          If provided, the graphml edge id is set by looking up the corresponding
          edge data attribute keyed by this parameter. If `None` or the key does not exist in edge data,
          the edge id is set by the edge key if `G` is a MultiGraph, else the edge id is left unset.
  
      Examples
      --------
      >>> G = nx.path_graph(4)
      >>> linefeed = chr(10)  # linefeed = \n
      >>> s = linefeed.join(nx.generate_graphml(G))
      >>> for line in nx.generate_graphml(G):  # doctest: +SKIP
      ...     print(line)
  
      Notes
      -----
      This implementation does not support mixed graphs (directed and unidirected
      edges together) hyperedges, nested graphs, or ports.
      """
      writer = GraphMLWriter(
          encoding=encoding,
          prettyprint=prettyprint,
          named_key_ids=named_key_ids,
          edge_id_from_attribute=edge_id_from_attribute,
      )
      writer.add_graph_element(G)
      yield from str(writer).splitlines()
  
imports: import warnings
  from collections import defaultdict
  import networkx
  from networkx.utils import open_file
label_desc: Use image node_id 3 for calling a global function with example usage: generate_graphml(G, encoding, prettyprint, named_key_ids, edge_id_from_attribute) without return types