Update SobelFilter.py
Update SobelFilter.py

mathturtle/tomviz,cjh1/tomviz,thewtex/tomviz,cryos/tomviz,mathturtle/tomviz,mathturtle/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,cjh1/tomviz,cryos/tomviz,cryos/tomviz,thewtex/tomviz,OpenChemistry/tomviz,thewtex/tomviz,cjh1/tomviz,OpenChemistry/tomviz