code: def __init__(self, toolmanager):
      ToolContainerBase.__init__(self, toolmanager)
      Gtk.Box.__init__(self)
      self.set_property("orientation", Gtk.Orientation.HORIZONTAL)
  
      # Tool items are created later, but must appear before the message.
      self._tool_box = Gtk.Box()
      self.append(self._tool_box)
      self._groups = {}
      self._toolitems = {}
  
      # This filler item ensures the toolbar is always at least two text
      # lines high. Otherwise the canvas gets redrawn as the mouse hovers
      # over images because those use two-line messages which resize the
      # toolbar.
      label = Gtk.Label()
      label.set_markup(
          "<small>\N{NO-BREAK SPACE}\n\N{NO-BREAK SPACE}</small>"
      )
      label.set_hexpand(True)  # Push real message to the right.
      self.append(label)
  
      self._message = Gtk.Label()
      self._message.set_justify(Gtk.Justification.RIGHT)
      self.append(self._message)
  
imports: import functools
  import io
  import os
  import matplotlib
  from matplotlib import _api, backend_tools, cbook
  from matplotlib.backend_bases import ToolContainerBase, KeyEvent, LocationEvent, MouseEvent, ResizeEvent, CloseEvent
  from gi.repository import Gio, GLib, Gtk, Gdk, GdkPixbuf
  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 ToolbarGTK4 object from inherited base classes: ToolContainerBase, Gtk with example: obj = ToolbarGTK4(toolmanager)