code: def width_max(self, width_max):
          
          if width_max is None:
              self._width_limits[1] = None
              return
  
          width_max = float(width_max)
          assert(self.width_min <= width_max)
  
          self._width_limits[1] = width_max
          self._update_layout()
docs: Set the maximum width of the widget.
  
          Parameters
          ----------
          width_max: None | float
              the maximum width of the widget. if None, maximum width
              is unbounded