def METHOD_NAME(self) -> None:
    name = self.name.get()
    if name not in self.app.core.custom_observers:
        cmd = self.cmd.get()
        observer = Observer(name, cmd)
        self.app.core.custom_observers[name] = observer
        self.observers.insert(tk.END, name)
        self.name.set("")
        self.cmd.set("")
        self.app.menubar.observers_menu.draw_custom()
        self.app.toolbar.observers_menu.draw_custom()
    else:
        messagebox.showerror("Observer Error", f"{name} already exists")