class_docstr: Knob - simple class with a "setKnob" method.
  A Knob instance is attached to a Param instance, e.g., param.attach(knob)
  Base class is for documentation purposes.
code: def setKnob(self, value):
      pass
  
imports: import wx
  import numpy
  from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg
  from matplotlib.figure import Figure
label_desc: Use image node_id 1 for calling the Knob obj's underlying member method code with example usage: obj.setKnob(value) without return types