Set sizers

def _do_layout(self):
        """Set sizers"""

        sizer_dialog = wx.FlexGridSizer(3, 1, 0, 0)

        # Sub sizers
        sizer_buttons = wx.FlexGridSizer(1, 3, 5, 5)

        # Adding buttons to sizer_buttons
        for button in [self.button_cancel, self.button_apply, self.button_ok]:
            sizer_buttons.Add(button, 0, wx.ALL | wx.EXPAND, 5)

        sizer_buttons.AddGrowableRow(0)
        for col in xrange(3):
            sizer_buttons.AddGrowableCol(col)

        # Adding main components
        sizer_dialog.Add(self.csvwidgets.sizer_csvoptions,
                         0, wx.ALL | wx.EXPAND, 5)
        sizer_dialog.Add(self.preview_textctrl,  1, wx.ALL | wx.EXPAND, 0)
        sizer_dialog.Add(sizer_buttons,  0, wx.ALL | wx.EXPAND, 5)

        self.SetSizer(sizer_dialog)

        sizer_dialog.AddGrowableRow(1)
        sizer_dialog.AddGrowableCol(0)

        self.Layout()
        self.Centre()