code: def set_history_buttons(self):
      can_backward = self._nav_stack._pos > 0
      can_forward = self._nav_stack._pos < len(self._nav_stack) - 1
      if "Back" in self._gtk_ids:
          self._gtk_ids["Back"].set_sensitive(can_backward)
      if "Forward" in self._gtk_ids:
          self._gtk_ids["Forward"].set_sensitive(can_forward)
  
imports: import logging
  import sys
  import matplotlib
  from matplotlib import _api, backend_tools, cbook
  from matplotlib._pylab_helpers import Gcf
  from matplotlib.backend_bases import _Backend, FigureCanvasBase, FigureManagerBase, NavigationToolbar2, TimerBase
  from matplotlib.backend_tools import Cursors
  import gi
  from gi.repository import Gdk, Gio, GLib, Gtk
label_desc: Use image node_id 7 for calling the _NavigationToolbar2GTK obj's underlying member method code with example usage: obj.set_history_buttons() without return types