remove dead code and unused imports from segmentation.py
remove dead code and unused imports from segmentation.py

openhumanoids/director,patmarion/director,manuelli/director,manuelli/director,openhumanoids/director,patmarion/director,openhumanoids/director,mitdrc/director,patmarion/director,patmarion/director,mitdrc/director,manuelli/director,openhumanoids/director,manuelli/director,patmarion/director,manuelli/director,mitdrc/director,openhumanoids/director,mitdrc/director,mitdrc/director