[graph-tool] New to graphtool , coming from networkx. Any support for json?

Hello Graph-Tool I had experience with networkx , but due to performance requirements i am thinking about trying graph-tool. My main goal it to generate network graph for email communications , but i need to make it available online as interactive networks so i want to know if json serialization available? I will use sigma.js http://sigmajs.org/ to render network graphs like this : http://exploringdata.github.io/info/npm-packages-dependencies/ I would be very grateful if i can have pointers for that. Thanks Phyo.