code: def addButton(
      fnc,
      states=("On", "Off"),
      c=("w", "w"),
      bc=("dg", "dr"),
      pos=(20, 40),
      size=24,
      font="arial",
      bold=False,
      italic=False,
      alpha=1,
      angle=0,
  ):
      
      vp = settings.plotter_instance
      if not vp.renderer:
          colors.printc("~timesError: Use addButton() after rendering the scene.", c=1)
          return
      import vtkplotter.vtkio as vtkio
      bu = vtkio.Button(fnc, states, c, bc, pos, size, font, bold, italic, alpha, angle)
      vp.renderer.AddActor2D(bu.actor)
      vp.window.Render()
      vp.buttons.append(bu)
      return bu
docs: Add a button to the renderer window.
      
      :param list states: a list of possible states ['On', 'Off']
      :param c:      a list of colors for each state
      :param bc:     a list of background colors for each state
      :param pos:    2D position in pixels from left-bottom corner
      :param size:   size of button font
      :param str font:   font type (arial, courier, times)
      :param bool bold:   bold face (False)
      :param bool italic: italic face (False)
      :param float alpha:  opacity level
      :param float angle:  anticlockwise rotation in degrees
  
      .. hint:: |buttons| |buttons.py|_