networkx gexf version 1.3 convert 1.2
<gexf version="1.2" xmlns="http://www.gexf.net/1.2draft"
xmlns:viz="http://www.gexf.net/1.2/viz"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.gexf.net/1.2draft
http://www.gexf.net/1.2draft/gexf.xsd">