more on python type hint

daemon/core/gui/dialogs/about.py

@@ -1,9 +1,13 @@
 import tkinter as tk
 from tkinter import ttk
+from typing import TYPE_CHECKING
 
 from core.gui.dialogs.dialog import Dialog
 from core.gui.widgets import CodeText
 
+if TYPE_CHECKING:
+    from core.gui.app import Application
+
 LICENSE = """\
 Copyright (c) 2005-2020, the Boeing Company.
 
@@ -31,7 +35,7 @@ THE POSSIBILITY OF SUCH DAMAGE.\
 
 
 class AboutDialog(Dialog):
-    def __init__(self, master, app):
+    def __init__(self, master: tk.Widget, app: "Application"):
         super().__init__(master, app, "About CORE", modal=True)
         self.draw()