def add_child key, page = nil
      if key.is_a? Page
        page, key = key, (self.keys.length + 1).to_sym
      end
      page.parent = self
      page.url = key
      self[key] = page
    end
def add_child key, page = nil
      if key.is_a? Page
        page, key = key, (self.keys.length + 1).to_sym
      end
      page.parent = self
      page.url = key
      self[key] = page
    end
Add a child page. You will seldom need to call this directly.
 Instead use add_blog or add_article