'Draw a `Selection Dialog` on screen used to make configurations.
:param pos: Index of selected item in `Configure Setting` frame.
:type pos: int
.. warning:: The value of `pos` MUST NOT be `None`.
:return: A **WindowObject** which represents the selection dialog.
:rtype: WindowObject'

def sub_selection_dialog(self, pos):

    i_len = len(self.settings[pos][2])
    shadow = curses.newwin((i_len + 2), 18, (13 - (i_len / 2)), 31)
    shadow.bkgd('    ', curses.color_pair(8))
    shadow.refresh()
    screen = curses.newwin((i_len + 2), 18, (12 - (i_len / 2)), 30)
    screen.box()
    screen.bkgd('    ', curses.color_pair(1))
    screen.keypad(1)
    normal = curses.A_NORMAL
    screen.addstr(0, 3, self.settings[pos][0].center(12), normal)
    return screen
