code: def __init__(self, toolmanager):
      ToolContainerBase.__init__(self, toolmanager)
      Gtk.Box.__init__(self)
      self.set_property("orientation", Gtk.Orientation.HORIZONTAL)
      self._message = Gtk.Label()
      self._message.set_justify(Gtk.Justification.RIGHT)
      self.pack_end(self._message, False, False, 0)
      self.show_all()
      self._groups = {}
      self._toolitems = {}
  
imports: import functools
  import logging
  import os
  from pathlib import Path
  import matplotlib
  from matplotlib import _api, backend_tools, cbook
  from matplotlib.backend_bases import ToolContainerBase, CloseEvent, KeyEvent, LocationEvent, MouseEvent, ResizeEvent
  from gi.repository import Gio, GLib, GObject, Gtk, Gdk
  from .None import _backend_gtk
  from ._backend_gtk import _BackendGTK, _FigureCanvasGTK, _FigureManagerGTK, _NavigationToolbar2GTK, TimerGTK
label_desc: Use image node_id 1 to create a new ToolbarGTK3 object from inherited base classes: ToolContainerBase, Gtk with example: obj = ToolbarGTK3(toolmanager)