Virtual python shell with Vte.Pty.spawn_async()

I would like add virtual python shell with Vte to my GTK3.0 python3 app and I am able to do this with spawn_sync() method, but this method is deprecated, so I would like to do it with preferred way with Vte.Pty.spawn_async(), but I dont understeand how .... I tried some parts of code, but with no luck. Pleas, give me someone some working code in python. For example, I tried variant like this:

import gi
gi.require_version('Gtk', '3.0')
gi.require_version('Vte', '2.91')
from gi.repository import Gtk, Vte

    class TheWindow(Gtk.Window):
        def __init__(self):
            Gtk.Window.__init__(self, title="GTK3 IDE")
            self.set_default_size(600, 300)

            self.terminal = Vte.Terminal()
            self.pty = self.terminal.pty_new_sync(Vte.PtyFlags.DEFAULT)
            #self.pty.child_setup()
            #self.pty = Vte.Pty(fd=-1)
            #self.pty.new_sync(Vte.PtyFlags.DEFAULT, None)

            self.pty.spawn_async(
                None,
                ["/bin/python"],
                None,
                GLib.SpawnFlags.DO_NOT_REAP_CHILD,
                None,
                None,
                -1,
                None,
                self.ready
                )

        def ready(self, pty, task):
            print('pty ', pty)

            self.terminal.set_pty(self.pty)

            box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)

            scroller = Gtk.ScrolledWindow()
            scroller.set_hexpand(True)
            scroller.set_vexpand(True)
            scroller.add(self.terminal)
            box.pack_start(scroller, False, True, 2)
            self.add(box)

    win=TheWindow()
    win.connect('destroy', Gtk.main_quit)
    win.show_all()
    Gtk.main()

There is final working solution, I made bad mistakes, now it is working great :). Thanks @elya5 for your answer :).

import gi
gi.require_version('Gtk', '3.0')
gi.require_version('Vte', '2.91')
from gi.repository import Gtk, Vte, GLib, Pango, Gio

    class TheWindow(Gtk.Window):
        def __init__(self):
            Gtk.Window.__init__(self, title="GTK3 IDE")
            self.set_default_size(600, 300)

            terminal = Vte.Terminal()
            #pty = terminal.pty_new_sync(Vte.PtyFlags.DEFAULT)
            pty = Vte.Pty.new_sync(Vte.PtyFlags.DEFAULT)
            terminal.set_pty(pty)

            pty.spawn_async(
                None,
                ["/bin/python"],
                None,
                GLib.SpawnFlags.DO_NOT_REAP_CHILD,
                None,
                None,
                -1,
                None,
                self.ready
                )

            #self.terminal.get_pty(self.pty)

            box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)

            scroller = Gtk.ScrolledWindow()
            scroller.set_hexpand(True)
            scroller.set_vexpand(True)
            scroller.add(terminal)
            box.pack_start(scroller, False, True, 2)
            self.add(box)

        def ready(self, pty, task):
            print('pty ', pty)


    win=TheWindow()
    win.connect('destroy', Gtk.main_quit)
    win.show_all()
    Gtk.main()