avoid lookup in setattr
avoid lookup in setattr

jupyter-widgets/ipywidgets,cornhundred/ipywidgets,SylvainCorlay/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,cornhundred/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,cornhundred/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,SylvainCorlay/ipywidgets,cornhundred/ipywidgets,jupyter-widgets/ipywidgets,cornhundred/ipywidgets,jupyter-widgets/ipywidgets