code: def mouseDown(self, event):
      if self.lines[0].contains(event)[0]:
          self.state = "frequency"
      elif self.lines[1].contains(event)[0]:
          self.state = "time"
      else:
          self.state = ""
      self.mouseInfo = (
          event.xdata,
          event.ydata,
          max(self.f0.value, 0.1),
          self.A.value,
      )
  
imports: import wx
  import numpy
  from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg
  from matplotlib.figure import Figure
label_desc: Use image node_id 4 for calling the FourierDemoFrame obj's underlying member method code with example usage: obj.mouseDown(event) without return types