fix bug in benchmark
fix bug in benchmark

lilleswing/deepchem,lilleswing/deepchem,lilleswing/deepchem,ktaneishi/deepchem,miaecle/deepchem,peastman/deepchem,miaecle/deepchem,Agent007/deepchem,ktaneishi/deepchem,deepchem/deepchem,deepchem/deepchem,peastman/deepchem,ktaneishi/deepchem,Agent007/deepchem,Agent007/deepchem,rbharath/deepchem,miaecle/deepchem,rbharath/deepchem