Reads the HOTKEYS global variable and insert all data in
        the TreeStore used by the preferences window treeview.

def populate_keys_tree(self):
        """Reads the HOTKEYS global variable and insert all data in
        the TreeStore used by the preferences window treeview.
        """
        for group in HOTKEYS:
            parent = self.store.append(None, [None, group['label'], None, None])
            for item in group['keys']:
                if item['key'] == "show-hide" or item['key'] == "show-focus":
                    accel = self.settings.keybindingsGlobal.get_string(item['key'])
                else:
                    accel = self.settings.keybindingsLocal.get_string(item['key'])
                gsettings_path = item['key']
                keycode, mask = Gtk.accelerator_parse(accel)
                keylabel = Gtk.accelerator_get_label(keycode, mask)
                self.store.append(parent, [gsettings_path, item['label'], keylabel, accel])
        self.get_widget('treeview-keys').expand_all()