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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_page(self, page, default = True):
 r""" Add a display page to the display. :param page: Page to be added :type display_id: ``DisplayPage`` :param default: True if this page should be shown upon initialization. :type name: ``bool`` """

        self._pages[page.page_id] = page
        page._add_display(self)
        if default or not self._active_page:
            self._active_page = page