code: def width(self, w):
      self._width = w
      self.fshader["isowidth"] = float(w)
  
imports: from .base_filter import Filter
  from ..shaders import Function, Varying
  from ...color import colormap, Color
label_desc: Use image node_id 5 for calling the IsolineFilter obj's underlying member method code with example usage: obj.width(w) without return types