Python 2.7 无法读取networkx中已由networkx nx写入的Graphml。写入\u Graphml

我使用nx.write\u graphml编写了一个graphml文件，但是当我试图读回它时，我得到了以下错误

>>> g = nx.DiGraph()
>>> g = nx.read_graphml('cit89.graphml')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 2, in read_graphml
  File "/usr/local/lib/python2.7/dist-packages/networkx/utils/decorators.py", line 220, in _open_file
    result = func(*new_args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/networkx/readwrite/graphml.py", line 153, in read_graphml
    glist=list(reader(path=path))
  File "/usr/local/lib/python2.7/dist-packages/networkx/readwrite/graphml.py", line 405, in __call__
    yield self.make_graph(g, keys, defaults)
  File "/usr/local/lib/python2.7/dist-packages/networkx/readwrite/graphml.py", line 431, in make_graph
    self.add_node(G, node_xml, graphml_keys)
  File "/usr/local/lib/python2.7/dist-packages/networkx/readwrite/graphml.py", line 456, in add_node
    node_id = self.node_type(node_xml.get("id"))
UnicodeEncodeError: 'ascii' codec can't encode characters in position 1-2: ordinal not in range(128)

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请提供您试图读取的文件，或者提供一个简短的生成错误的自包含示例。该文件包含节点ID，如，以及更多关于2*10^5和一百万条边的信息…………plz帮助也许您可以将其精简为一个显示问题的完整示例？显然，字符编码存在一些问题。