tkinter: how to get a string from any Text widget in which the Menu widget is called (cursor is on, text is selected)

Question

Python

Actually, there is an example , when a key is bound to an Entry instance and the line is obtained as follows
event.widget.get()
:
a link to pastebin , a link to dumpz with more kosher highlighting and fonts.
As far as I understand, when adding a command to the Menu widget, a bind is not possible.
In this code, when using the copy function from the menu, an error is generated.
AttributeError: 'Application' object has no attribute 'widget'
In all the examples that I dug up, including in the text editor example, the Text widget is one per frame (or within the class) and is accessed through self.
Occasionally a cowardly thought runs through that this functionality is not possible within Tkinter.
I hope this is just my ignorance.
Which way to look?