title: Adding wxpython panel classes to sizers
body: <p>I want to add panel classes to a sizer in a frame class that I will call in the main line of the code.</p>
  
  <p>The error I get is <code>TypeError: wx.Window, wx.Sizer, wx.Size, or (w,h) expected for item</code>. I assume this has to do with the fact that it is a panel class and not the instance of the panel class..</p>
  
  <p>Either way, how would I do such a thing?</p>
  
  <p>Code is below:</p>
  
  <pre><code>#!/usr/bin/python
  # -*- coding: utf-8 -*-
  
  import wx
  
  class step_1(wx.Panel):
      def __init__(self, parent):
          wx.Panel.__init__(self, parent, id=wx.ID_ANY)
  
          sizer = wx.BoxSizer(wx.VERTICAL)
          txtOne = wx.TextCtrl(self, wx.ID_ANY, "")
  
          sizer = wx.BoxSizer(wx.VERTICAL)
          sizer.Add(txtOne, 0, wx.ALL, 5)
  
          self.SetSizer(sizer)
  
  class step_2(wx.Panel):
      def __init__(self, parent):
          wx.Panel.__init__(self, parent, id=wx.ID_ANY)
  
          sizer = wx.BoxSizer(wx.VERTICAL)
          txtOne = wx.TextCtrl(self, wx.ID_ANY, "")
  
          sizer = wx.BoxSizer(wx.VERTICAL)
          sizer.Add(txtOne, 0, wx.ALL, 5)
  
          self.SetSizer(sizer)
  
  class main_frame(wx.Frame):
      """Main Frame holding the main panel."""
      def __init__(self,*args,**kwargs):
          wx.Frame.__init__(self,*args,**kwargs)
          p = wx.Panel(self)
          sizer = wx.BoxSizer(wx.VERTICAL)
          sizer.Add(step_1,0,border = 5)
          sizer.Add(step_2,0,border = 5)
          p.SetSizerAndFit(sizer)
          self.Show()
  
  if __name__ == "__main__":
      app = wx.App(False)
      frame = main_frame(None,-1,size = (400,300))
      app.MainLoop()
  </code></pre>