How to use the gooey.gui.util.wx_util function in Gooey

def __init__(self, parent):
    wx.Dialog.__init__(self, parent)

    self.SetBackgroundColour('#ffffff')

    self.ok_button = wx.Button(self, wx.ID_OK, label='Ok')
    self.datepicker = Classes.DatePickerCtrl(self, style=Constants.WX_DP_DROPDOWN)

    vertical_container = wx.BoxSizer(wx.VERTICAL)
    vertical_container.AddSpacer(10)
    vertical_container.Add(wx_util.h1(self, label='Select a Date'), 0, wx.LEFT | wx.RIGHT, 15)
    vertical_container.AddSpacer(10)
    vertical_container.Add(self.datepicker, 0, wx.EXPAND | wx.LEFT | wx.RIGHT, 15)

    vertical_container.AddSpacer(10)
    button_sizer = wx.BoxSizer(wx.HORIZONTAL)
    button_sizer.AddStretchSpacer(1)
    button_sizer.Add(self.ok_button, 0)

    vertical_container.Add(button_sizer, 0, wx.LEFT | wx.RIGHT, 15)
    vertical_container.AddSpacer(20)
    self.SetSizerAndFit(vertical_container)

    self.Bind(wx.EVT_BUTTON, self.OnOkButton, self.ok_button)

def __init__(self, parent):
    wx.Dialog.__init__(self, parent)

    self.SetBackgroundColour('#ffffff')

    self.ok_button = wx.Button(self, wx.ID_OK, label=_('Ok'))
    self.datepicker = Classes.DatePickerCtrl(self, style=Constants.WX_DP_DROPDOWN)

    vertical_container = wx.BoxSizer(wx.VERTICAL)
    vertical_container.AddSpacer(10)
    vertical_container.Add(wx_util.h1(self, label=_('Select a Date')), 0, wx.LEFT | wx.RIGHT, 15)
    vertical_container.AddSpacer(10)
    vertical_container.Add(self.datepicker, 0, wx.EXPAND | wx.LEFT | wx.RIGHT, 15)

    vertical_container.AddSpacer(10)
    button_sizer = wx.BoxSizer(wx.HORIZONTAL)
    button_sizer.AddStretchSpacer(1)
    button_sizer.Add(self.ok_button, 0)

    vertical_container.Add(button_sizer, 0, wx.LEFT | wx.RIGHT, 15)
    vertical_container.AddSpacer(20)
    self.SetSizerAndFit(vertical_container)

    self.Bind(wx.EVT_BUTTON, self.OnOkButton, self.ok_button)

def _do_layout(self):
    sizer = wx.BoxSizer(wx.VERTICAL)
    sizer.Add(self.head_panel, 0, wx.EXPAND)
    sizer.Add(wx_util.horizontal_rule(self), 0, wx.EXPAND)

    if self.layout_type == layouts.COLUMN:
      self.config_panel = layouts.ColumnLayout(self)
    else:
      self.config_panel = layouts.FlatLayout(self)

    sizer.Add(self.config_panel, 1, wx.EXPAND)

    sizer.Add(self.runtime_display, 1, wx.EXPAND)

    self.runtime_display.Hide()
    sizer.Add(wx_util.horizontal_rule(self), 0, wx.EXPAND)
    sizer.Add(self.foot_panel, 0, wx.EXPAND)
    self.SetSizer(sizer)

    self.sizer = sizer

def layout(self, num_columns):
    STD_LAYOUT = (0, wx.LEFT | wx.RIGHT | wx.EXPAND, PADDING)

    if self.title:
      self.container.Add(wx_util.h0(self, self.title), 0, wx.LEFT | wx.RIGHT, PADDING)
      self.container.AddSpacer(30)

    if self.widgets:
      self.container.Add(wx_util.h1(self, self.section_name), 0, wx.LEFT | wx.RIGHT, PADDING)
      self.container.AddSpacer(5)
      self.container.Add(wx_util.horizontal_rule(self), *STD_LAYOUT)
      self.container.AddSpacer(20)
      self.create_component_grid(self.container, self.widgets, cols=num_columns)
      self.container.AddSpacer(10)

def arrange(self, *args, **kwargs):
        wx_util.make_bold(self.label)
        wx_util.withColor(self.label, self._options['label_color'])
        wx_util.withColor(self.help_text, self._options['help_color'])
        wx_util.withColor(self.error, self._options['error_color'])
        self.error.Hide()

        self.help_text.SetMinSize((0,-1))

        layout = wx.BoxSizer(wx.VERTICAL)

        if self._options.get('show_label', True):
            layout.Add(self.label, 0, wx.EXPAND)
        else:
            layout.AddStretchSpacer(1)

        layout.AddSpacer(2)
        if self.help_text and self._options.get('show_help', True):