Hi Donglin, welcome 
Please take the time to read the FAQ as this will help you get better responses
It looks like you would like the wall sweep to be the same material as the wall. This may work for a basic wall of one material, what if the wall has multiple materials?
Based on Revit modelling standard this Wall Sweep could also be modelled as a Wall which could be of the same type at a different thickness
If possible please provide some additional information of the purpose of your script and what you are trying to achieve