refine fobj and feval in sklearn interface
refine fobj and feval in sklearn interface

Laurae2/LightGBM,wxchan/LightGBM,wxchan/LightGBM,henry0312/LightGBM,cbecker/LightGBM,huanzhang12/lightgbm-gpu,microsoft/LightGBM,huanzhang12/lightgbm-gpu,Allardvm/LightGBM,huanzhang12/LightGBM,olofer/LightGBM,wxchan/LightGBM,olofer/LightGBM,huanzhang12/LightGBM,fstonezst/LightGBM,fstonezst/LightGBM,microsoft/LightGBM,Allardvm/LightGBM,huanzhang12/LightGBM,sightmachine/LightGBM,Laurae2/LightGBM,henry0312/LightGBM,olofer/LightGBM,huanzhang12/LightGBM,Laurae2/LightGBM,fstonezst/LightGBM,henry0312/LightGBM,fstonezst/LightGBM,sightmachine/LightGBM,cbecker/LightGBM,henry0312/LightGBM,sightmachine/LightGBM,Allardvm/LightGBM,Allardvm/LightGBM,henry0312/LightGBM,microsoft/LightGBM,huanzhang12/lightgbm-gpu,Allardvm/LightGBM,fstonezst/LightGBM,wxchan/LightGBM,wxchan/LightGBM,Laurae2/LightGBM,huanzhang12/lightgbm-gpu,olofer/LightGBM,microsoft/LightGBM,cbecker/LightGBM,huanzhang12/lightgbm-gpu,sightmachine/LightGBM,Laurae2/LightGBM,olofer/LightGBM,cbecker/LightGBM,microsoft/LightGBM,huanzhang12/LightGBM