fix graph example for python3
fix graph example for python3

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branch : python3

urwid/urwid,mountainstorm/urwid,westurner/urwid,westurner/urwid,rndusr/urwid,rndusr/urwid,tonycpsu/urwid,bk2204/urwid,tonycpsu/urwid,wardi/urwid,foreni-packages/urwid,drestebon/urwid,hkoof/urwid,wardi/urwid,ivanov/urwid,ivanov/urwid,hkoof/urwid,harlowja/urwid,mountainstorm/urwid,bk2204/urwid,drestebon/urwid,drestebon/urwid,inducer/urwid,harlowja/urwid,tonycpsu/urwid,harlowja/urwid,douglas-larocca/urwid,wardi/urwid,douglas-larocca/urwid,inducer/urwid,westurner/urwid,inducer/urwid,Julian/urwid,bk2204/urwid,foreni-packages/urwid,urwid/urwid,mountainstorm/urwid,Julian/urwid,rndusr/urwid,foreni-packages/urwid,zyga/urwid,zyga/urwid,hkoof/urwid,douglas-larocca/urwid,urwid/urwid,ivanov/urwid,Julian/urwid,zyga/urwid