code: def _draw_func(self, drawing_area, ctx, width, height):
      self.on_draw_event(self, ctx)
      self._post_draw(self, ctx)
  
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 18 for calling the FigureCanvasGTK4 obj's underlying member method code with example usage: obj._draw_func(drawing_area, ctx, width, height) without return types