code: def set_data(self, n_levels, cmap):
      self.iso.set_color(cmap)
      cl = np.linspace(-self.radius, self.radius, n_levels + 2)[1:-1]
      self.iso.levels = cl
  
file_path: vispy/examples/scene/isocurve_for_trisurface_qt.py
imports: import numpy
  from vispy import scene, app
  from vispy.geometry.generation import create_sphere
  from vispy.color.colormap import get_colormaps
label_desc: Use image node_id 2 for calling the Canvas obj's underlying member method code with example usage: obj.set_data(n_levels, cmap) without return types