I can make a widget inside another widget, as example an `urwid.Frame` father could have as `body` an `urwid.Pile` widget as child.
In this situation, the father should process some input keys when the child have to treat some specific others keys.

Like in this functional example:

```
import urwid

class NewFrame(urwid.Frame):
    def __init__(self, givenBody):
        super().__init__(urwid.Filler(givenBody, "top"))

    def keypress(self, size, key):
        if key  in ('f'):
            print("We are in NewFrame object")

        return super(NewFrame, self).keypress(size, key)

class NewPile(urwid.Pile):
    def __init__(self, givenList):
        super().__init__(givenList)

    def keypress(self, size, key):
        if key  in ('p'):
            print("We are in NewPile object")

        return super(NewPile, self).keypress(size, key)

master_pile = NewPile([
    urwid.Text("foo"),
    urwid.Divider(u'─'),
])

frame = NewFrame(master_pile)

loop = urwid.MainLoop(frame)
loop.run()

```

When I press `f` I could see the `Text` widget “We are in NewFrame”. But when I press `p`, the `NewPile` text doesn’t appear and nothing happens.

So, how could I make the child widget get input keys, especially when they are not matched by the `.keypress()` method of the parent?