ある Tkinter ページから別の Tkinter ページに StringVar データにアクセスするにはどうすればよいですか?

<code class="python">class PageOne(ttk.Frame):
    def __init__(self, parent, controller):
        self.controller = controller
        ...

class PageTwo(ttk.Frame):
    def __init__(self, parent, controller):
        self.controller = controller
        ...</code>

<code class="python">class MyApp(Tk):
    ...
    def get_page(self, classname):
        '''Returns an instance of a page given it's class name as a string'''
        for page in self.frames.values():
            if str(page.__class__.__name__) == classname:
                return page
        return None</code>

<code class="python">class PageTwo(ttk.Frame):
    ...
    def print_it(self):
        page_one = self.controller.get_page("PageOne")
        value = page_one.some_entry.get()
        print ('The value stored in StartPage some_entry = %s' % value)</code>

<code class="python">class MyApp(Tk):
    def __init__(self):
        ...
        self.app_data = {"name":    StringVar(),
                         "address": StringVar(),
                         ...
                        }</code>

<code class="python">class PageOne(ttk.Frame):
    def __init__(self, parent, controller):
        self.controller=controller
        ...
        self.some_entry = ttk.Entry(self,
            textvariable=self.controller.app_data["name"], ...) </code>

<code class="python">    def print_it(self):
        value = self.controller.app_data["address"].get()
        ...</code>