reverse the direction of arrows in xdot.py graphs without modifying the dot input

[Kartik Lakshminarasimhan]

Hi, 
I am trying to reverse the arrows in th edges of my graph. Say I have directed graph a-> b, b->c in graphviz dot format. But, I want the xdot.py to draw the graphs(with arrow head and tail reversed,) as b->a and c->b. Perhaps, it should be possible by modifying the vector graphics drawing functions(LINE_CAP_BUTT/LINE_JOIN_MITER). I was trying to modify the cairo functions(cr.*) in many classes by exchanging the x and y , src and dst. But, could not get it done It would be really helpful for me if anyone could point me the function/show how to do it. Any help would be much appreciated.