pydot can not print graph with special characters

[GoogleCodeExporter]

The following code shows that pydot can't print graph whose nodes consist of 
special characters. Is it a bug of pydot?

import pydot

graph = pydot.Dot(graph_type='graph')
graph.add_edge(pydot.Edge("<a>", "<b>"))
graph.add_edge(pydot.Edge("<a>", "<c>"))
graph.write_png('main1.png')

Original issue reported on code.google.com by PengYu...@gmail.com on 30 Nov 2013 at 3:00