code: def _add_button(self, button, group, position):
      if group not in self._groups:
          if self._groups:
              self._add_separator()
          group_box = Gtk.Box()
          self._tool_box.append(group_box)
          self._groups[group] = group_box
      self._groups[group].insert_child_after(
          button, self._find_child_at_position(group, position)
      )
  
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 4 for calling the ToolbarGTK4 obj's underlying member method code with example usage: obj._add_button(button, group, position) without return types