wxpython 中怎么显示位图的按钮~~~书上的例子是错的~求救？？？？

class BitmapButtonFrame(wx.Frame):
        def __init__(self):
            wx.Frame.__init__(self, None, -1, ’Bitmap Button Example’,size=(200, 150))
            panel = wx.Panel(self, -1)
            bmp = wx.Image(“bitmap.bmp”, wx.BITMAP_TYPE_BMP).ConvertToBitmap() #这里出错了~~~
            
            self.button = wx.BitmapButton(panel, -1, bmp, pos=(10, 20))
            self.Bind(wx.EVT_BUTTON, self.OnClick, self.button)
            self.button.SetDefault()
            self.button2 = wx.BitmapButton(panel, -1, bmp, pos=(100, 20),style=0)
            self.Bind(wx.EVT_BUTTON, self.OnClick, self.button2)

该怎么做才能 在按钮上显示位图呢？？？？