Minor fix to Transformer example
Minor fix to Transformer example

miaecle/deepchem,miaecle/deepchem,lilleswing/deepchem,lilleswing/deepchem,peastman/deepchem,lilleswing/deepchem,deepchem/deepchem,peastman/deepchem,deepchem/deepchem,miaecle/deepchem